Satellite Communication - 7

7/24/2019 Satellite Communication - 7

1/47

Satellite CommunicationSatellite CommunicationLecture 7Lecture 7

Two-way Interactive Communication for Fixed and Mobile Users


2/47

OverviewOverview

Two-way Interactive Communication for Fixed and Mobile Users Introduction to V!T "etwor#s for Interactive !$$lications %rinci$le of %rotocol Layerin& %rotocols su$$orted by V!T "etwor#s

atellite %oint to %oint Connectivity

atellite %oint to Multi$oint Connectivity

V!T tar "etwor#s !$$lications !rc'itecture

%ersonal Com$uter Inte&ration wit' t'e V!T

($eration of Multi$le !ccess %rotocols in V!Ts

Mobile atellite ervices


3/47

IntroductionIntroduction

V!T networ#s are com$osed of low-cost )art'stations for use in a wide variety oftelecommunications a$$lications*

Unli#e t'e $oint-to-multi$oint systems V!Ts are

two-way communications installations desi&ned toac'ieve interactivity over t'e satellite Interconnection wit' various terrestrial networ#s is

also a feature* Internet 'as ta#en over t'e role of t'e common

structure for inte&ratin& data communications fort'e ma+ority of a$$lications in informationtec'nolo&y ,IT*

T'is 'as rationali.ed t'e field to t'e $oint t'at asin&le $rotocol and interface standard $rovide

almost all of w'at an or&ani.ation needs*


4/47

Introduction (Contd.)Introduction (Contd.)

T'e same a$$roac' wor#s e/ually well forindividuals and t'e small office0'ome office,(1( environment*

atellite communications tec'nolo&y 'as ada$ted

to t'is new world as well* (ddly2 it was not until t'e early 3456s t'at satellite

systems found a direct $lace in t'is ex$andin&field*

T'e overridin& $rinci$le of t'e V!T is t'at it is a

small bidirectional )art' station t'at deliversinte&rated data2 voice2 and video services wit'in a$ac#a&e t'at is often cost +ustified w'en com$aredto terrestrial alternatives*


5/47


Today2 terrestrial co$$er2 fiber lines2 data routin&and switc'in& in con+unction wit' V!Ts $rovide afast and effective mix to advance t'e com$etitivestrate&y of many medium to lar&e businesses*

V!T networ#s also address t'e needs of smallbusinesses and individuals* T'e t'ree classic arc'itectures for IT networ#s are

'ost-based $rocessin& ,utili.in& centrali.ed lar&e-scale com$uters li#e mainframes2 $eer-to-$eer

networ#s ,usually em$loyin& minicom$uters orlar&e servers t'at are de$loyed at differentlocations to serve local re/uirements2 andclient0server networ#s ,w'ic' tie to&et'er $ersonalcom$uters2 servers2 and $eri$'erals usin& L!"s and!"s*


6/47


T'e t'ree classic arc'itectures for IT networ#s are8

1ost-based $rocessin& ,utili.in& centrali.edlar&e-scale com$uters li#e mainframes2

%eer-to-$eer networ#s ,usually em$loyin&minicom$uters or lar&e servers t'at arede$loyed at different locations to serve localre/uirements2 and

Client0erver networ#s ,w'ic' tie to&et'er

$ersonal com$uters2 servers2 and $eri$'eralsusin& L!"s and !"s*

V!T networ#s now address t'e needs of smallbusinesses and individuals in all t'ese areas*


7/47

Principle of Protocol LayeringPrinciple of Protocol Layering

Modern data communications t'eory and $racticeModern data communications t'eory and $racticeis literally built u$on t'e conce$t of $rotocolis literally built u$on t'e conce$t of $rotocollayerin&2 w'ere t'e most basic transmissionlayerin&2 w'ere t'e most basic transmissionre/uirement is at t'e bottom and more com$lexre/uirement is at t'e bottom and more com$lex

and so$'isticated features are added one on to$ ofand so$'isticated features are added one on to$ ofeac' ot'er*eac' ot'er*

'ile t'is conce$t is abstract2 it is im$ortant to'ile t'is conce$t is abstract2 it is im$ortant tounderstandin& 'ow t'e data in a networ# isunderstandin& 'ow t'e data in a networ# isassembled2 $rocessed2 and reliably transferredassembled2 $rocessed2 and reliably transferredbetween sender and receiver*between sender and receiver*


8/47


It 'as evolved over decades of telecommunicationsIt 'as evolved over decades of telecommunicationsdevelo$ment2 be&innin& wit' t'e most sim$ledevelo$ment2 be&innin& wit' t'e most sim$levoice radiotele$'one networ#2 t'rou&' networ#svoice radiotele$'one networ#2 t'rou&' networ#st'at su$$ort national air defense2 a$$lied int'at su$$ort national air defense2 a$$lied in

business for lar&e-scale data $rocessin&2 andbusiness for lar&e-scale data $rocessin&2 andevolved into t'e $ervasive structure of t'eevolved into t'e $ervasive structure of t'eInternet*Internet*

T'e layerin& conce$t is embodied in t'e ($enT'e layerin& conce$t is embodied in t'e ($enystems Interconnection ,(I model s'own inystems Interconnection ,(I model s'own inFi&ure 5*3 and contained in relevant standards ofFi&ure 5*3 and contained in relevant standards oft'e International tandards (r&ani.ation ,I(t'e International tandards (r&ani.ation ,I(and t'e ITU-Telecommunication ector ,ITU-T*and t'e ITU-Telecommunication ector ,ITU-T*


9/47

OSI and TCP/IP (D!P) "odelOSI and TCP/IP (D!P) "odel


10/47


Layer 32 $'ysical8 $rovides t'e mec'anism forLayer 32 $'ysical8 $rovides t'e mec'anism fortransmittin& raw bits over t'e communicationtransmittin& raw bits over t'e communicationmedium ,e*&*2 fiber2 wireless2 and satellite*medium ,e*&*2 fiber2 wireless2 and satellite*

It s$ecifies t'e functional2 electrical2 andIt s$ecifies t'e functional2 electrical2 and

$rocedural c'aracteristics suc' as si&nal timin&2$rocedural c'aracteristics suc' as si&nal timin&2volta&e levels2 connector ty$e2 and use of $ins*volta&e levels2 connector ty$e2 and use of $ins*

T'e familiar 9-:;: connector definition is a &oodT'e familiar 9-:;: connector definition is a &oodexam$le of t'e $'ysical layer*exam$le of t'e $'ysical layer*

! way to loo# at t'is is t'at t'e $'ysical layer! way to loo# at t'is is t'at t'e $'ysical layerta#es t'e raw bit stream at t'e sendin& end andta#es t'e raw bit stream at t'e sendin& end andintroduces it to t'e networ#*introduces it to t'e networ#*

!ll to&et'er2 most of t'e investment in a satellite!ll to&et'er2 most of t'e investment in a satellite

networ# is at t'e $'ysical layer*networ# is at t'e $'ysical layer*


11/47


Layer :2 data lin#8 $rovides for t'e transfer of data betweenLayer :2 data lin#8 $rovides for t'e transfer of data betweenad+acent nodes or connection $oints eit'er by a dedicatedad+acent nodes or connection $oints eit'er by a dedicated$oint-to-$oint line ,e*&*2 a T3 $rivate line or a satellite du$lex$oint-to-$oint line ,e*&*2 a T3 $rivate line or a satellite du$lexlin# or a medium ca$able of s'ared bandwidt' ,e*&*2 anlin# or a medium ca$able of s'ared bandwidt' ,e*&*2 an)t'ernet cable or satellite T


12/47

Principle of Protocol LayeringPrinciple of Protocol Layering Layer =2 trans$ort8 $rovides anot'er level of assurance t'at t'eLayer =2 trans$ort8 $rovides anot'er level of assurance t'at t'e

information will $ro$erly traverse t'e networ#2 fromend user toinformation will $ro$erly traverse t'e networ#2 fromend user toend user*end user*

Two services are commonly available8 connectionless2 w'ic'Two services are commonly available8 connectionless2 w'ic'transfers $ac#ets of data2 one at a time> and connectiontransfers $ac#ets of data2 one at a time> and connectionoriented2 w'ere a virtual circuit is first establis'ed beforeoriented2 w'ere a virtual circuit is first establis'ed before

sendin& multi$le $ac#ets t'at ma#e u$ t'e entire conversation*sendin& multi$le $ac#ets t'at ma#e u$ t'e entire conversation* T'e familiar TC% layer of TC%0I% $rovides a connection-orientedT'e familiar TC% layer of TC%0I% $rovides a connection-oriented

service to com$uter a$$lications*service to com$uter a$$lications*

Layer ?2 session8 somew'at more com$licated t'an layers ; andLayer ?2 session8 somew'at more com$licated t'an layers ; and= but $rovided to instill yet &reater de&rees of reliability and= but $rovided to instill yet &reater de&rees of reliability and

convenience of interface to a$$lications*convenience of interface to a$$lications*

It mana&es t'e data exc'an&e between com$uter systems in anIt mana&es t'e data exc'an&e between com$uter systems in anorderly fas'ion to $rovide full-du$lex or 'alf-du$lexorderly fas'ion to $rovide full-du$lex or 'alf-du$lexconversations*conversations*

(ne im$ortant service is t'at of reestablis'in& t'e connection in(ne im$ortant service is t'at of reestablis'in& t'e connection int'e event t'at t'e trans$ort layer is interru$ted for some reason*t'e event t'at t'e trans$ort layer is interru$ted for some reason*


13/47


Layer @2 $resentation8 $rovides syntactic and semanticLayer @2 $resentation8 $rovides syntactic and semanticservices to t'e a$$lication layer above*services to t'e a$$lication layer above*

T'e $resentation layer is inserted to resolve t'e com$lexitiesT'e $resentation layer is inserted to resolve t'e com$lexitiesbetween trans$ort0networ# layers and t'e more sim$listicbetween trans$ort0networ# layers and t'e more sim$listicneeds of t'e actual a$$lication t'at em$loys t'e networ# inneeds of t'e actual a$$lication t'at em$loys t'e networ# in

t'e first $lace*t'e first $lace* ome s$eciali.ed services li#e encry$tion and data structureome s$eciali.ed services li#e encry$tion and data structure

definition are considered to be $art of t'e $resentation layer*definition are considered to be $art of t'e $resentation layer*

Interaction of t'e $resentation layer wit' elements of aInteraction of t'e $resentation layer wit' elements of asatellite networ# may cause incom$atibility2 re/uirin&satellite networ# may cause incom$atibility2 re/uirin&

additional $rocessin& to be $erformed in )art' stationadditional $rocessin& to be $erformed in )art' statione/ui$ment or user terminals*e/ui$ment or user terminals*


14/47


Layer 72 a$$lication8 includes t'e actual data communicationLayer 72 a$$lication8 includes t'e actual data communicationa$$lications t'at are common in o$en systems2 suc' as filea$$lications t'at are common in o$en systems2 suc' as filetransfer2 virtual terminal2 e-mail2 and remote databasetransfer2 virtual terminal2 e-mail2 and remote databaseaccess*access*

e refer to t'ese as a$$lications because t'ey include note refer to t'ese as a$$lications because t'ey include not

only t'e $rotocol elements t'at su$$ort s$ecific ty$es ofonly t'e $rotocol elements t'at su$$ort s$ecific ty$es ofinformation but also features and facilities t'at ultimatelyinformation but also features and facilities t'at ultimatelyinteract wit' t'e end user*interact wit' t'e end user*

Most non-ex$ert users will not use t'e a$$lication layerMost non-ex$ert users will not use t'e a$$lication layerdirectly2 instead relyin& on s$eciali.ed software wit'in t'edirectly2 instead relyin& on s$eciali.ed software wit'in t'ecom$uter to im$rove t'e interface and functionality*com$uter to im$rove t'e interface and functionality*

For exam$le2 most subscribers to on-line information servicesFor exam$le2 most subscribers to on-line information servicesuse t'e e-mail $ac#a&e su$$lied by t'e $rovider*use t'e e-mail $ac#a&e su$$lied by t'e $rovider*

T'is $ac#a&e2 in turn2 will en&a&e layer 7 e-mail services toT'is $ac#a&e2 in turn2 will en&a&e layer 7 e-mail services todo t'e actual function of sendin& and receivin& messa&edo t'e actual function of sendin& and receivin& messa&etraffic*traffic*


15/47


T'e V!T networ# is ideal for centrali.ed com$uter networ#sT'e V!T networ# is ideal for centrali.ed com$uter networ#sAt'at is2 t'ose t'at em$loy a 'ost com$uter*At'at is2 t'ose t'at em$loy a 'ost com$uter*

T'e ma+ority of suc' installations are assembled fromT'e ma+ority of suc' installations are assembled fromstandard com$uter com$onents su$$lied in t'e United tatesstandard com$uter com$onents su$$lied in t'e United tatesby by

Ma+or )uro$ean and a$anese su$$liers li#e Bull2 iemens2Ma+or )uro$ean and a$anese su$$liers li#e Bull2 iemens2Fu+itsu2 and 1itac'i are in t'is mar#et as well*Fu+itsu2 and 1itac'i are in t'is mar#et as well*

Followin& t'e layerin& conce$t2 eac' com$utin& or terminalFollowin& t'e layerin& conce$t2 eac' com$utin& or terminaldevice in t'e networ# 'as a uni/ue address t'at identifiesdevice in t'e networ# 'as a uni/ue address t'at identifiest'at device at t'e s$ecified layer*t'at device at t'e s$ecified layer*

ome exam$les of addressin& sc'emes are &iven in Table 5*3ome exam$les of addressin& sc'emes are &iven in Table 5*3


16/47



17/47

Protocol# #upported $y %ST &etwor'#Protocol# #upported $y %ST &etwor'#

! summary of t'e $rotocols in &eneral use and t'eir su$$ort! summary of t'e $rotocols in &eneral use and t'eir su$$ortover ty$ical V!T networ#s is $rovided in Table 5*:*over ty$ical V!T networ#s is $rovided in Table 5*:*

'en first introduced in t'e 3456s2 V!Ts $layed 'eavily on'en first introduced in t'e 3456s2 V!Ts $layed 'eavily ont'e traditional IBM $ro$rietary $rotocol2 ystems "etwor#t'e traditional IBM $ro$rietary $rotocol2 ystems "etwor#!rc'itecture ,"!2 w'ic' followed t'e same centrali.ed!rc'itecture ,"!2 w'ic' followed t'e same centrali.ed

a$$roac' as t'e V!T star networ#*a$$roac' as t'e V!T star networ#* 'ile still in existence in some le&acy environments2 it 'as'ile still in existence in some le&acy environments2 it 'as

been re$laced wit' t'e more o$en Internet %rotocol suitebeen re$laced wit' t'e more o$en Internet %rotocol suite,TC%0I%*,TC%0I%*

TC%0I% 'as its s'ortcomin&s2 w'ic' are bein& addressed byTC%0I% 'as its s'ortcomin&s2 w'ic' are bein& addressed by

standards bodies and ma+or vendors li#e Cisco*standards bodies and ma+or vendors li#e Cisco* )m$loyin& TC%0I% in a $rivate networ# is very)m$loyin& TC%0I% in a $rivate networ# is very

strai&'tforward and is well wit'in t'e means of anystrai&'tforward and is well wit'in t'e means of anyor&ani.ation or individual*or&ani.ation or individual*


18/47

Protocol# #upported $y %ST &etwor'#Protocol# #upported $y %ST &etwor'#


19/47

Protocol# #upported $y %ST &etwor'#Protocol# #upported $y %ST &etwor'# 1owever2 t'e com$lexity comes w'en an or&ani.ation wis'es1owever2 t'e com$lexity comes w'en an or&ani.ation wis'es

to interconnect wit' t'e &lobal Internet and wit' ot'erto interconnect wit' t'e &lobal Internet and wit' ot'eror&ani.ations*or&ani.ations*

T'is is due to t'e somew'at com$lex nature of routin&T'is is due to t'e somew'at com$lex nature of routin&$rotocols li#e t'e Border Dateway %rotocol ,BD% and a new$rotocols li#e t'e Border Dateway %rotocol ,BD% and a newsc'eme called Multi %rotocol Label witc'in& ,M%L*sc'eme called Multi %rotocol Label witc'in& ,M%L*

Frame 9elay 'as been $o$ular in !"s for more t'an aFrame 9elay 'as been $o$ular in !"s for more t'an adecade2 t'an#s to its ease of interface at t'e router anddecade2 t'an#s to its ease of interface at t'e router andavailability in ,and between ma+or countries*availability in ,and between ma+or countries*

It is ca$able of near-real-time transfer and can su$$ort voiceIt is ca$able of near-real-time transfer and can su$$ort voiceservices* it' access s$eeds &enerally available at : Mb$s orservices* it' access s$eeds &enerally available at : Mb$s or

less*less* atellite $rovision of Frame 9elay 'as been limited to $oint-atellite $rovision of Frame 9elay 'as been limited to $oint-

to-$oint circuits as t'e $rotocol is not directly su$$orted into-$oint circuits as t'e $rotocol is not directly su$$orted inV!Ts currently on t'e mar#et*V!Ts currently on t'e mar#et*

T'e best a$$roac' would be to use TC%0I% in lieu of FrameT'e best a$$roac' would be to use TC%0I% in lieu of Frame

9elay w'en V!T lin#s are interfaced at t'e router*9elay w'en V!T lin#s are interfaced at t'e router*


20/47

Satellite Point to Point ConnectivitySatellite Point to Point Connectivity

T'e first satellite networ#s to be im$lemented wereT'e first satellite networ#s to be im$lemented wereem$loyed for $oint-to-$oint connectivity to com$lementem$loyed for $oint-to-$oint connectivity to com$lementt'e cross-country microwave and undersea cable lin#st'e cross-country microwave and undersea cable lin#sof t'e time*of t'e time*

T'is to$olo&y remains an effective means ofT'is to$olo&y remains an effective means oftransferrin& information wit' minimum delay betweentransferrin& information wit' minimum delay between$airs of $oints*$airs of $oints*

!s illustrated in Fi&ure 5*:2 node 3 in a $oint-to-$oint!s illustrated in Fi&ure 5*:2 node 3 in a $oint-to-$ointservice conducts a full-du$lex conversation wit' node :service conducts a full-du$lex conversation wit' node :

,s'own wit' 'eavy arrows2 and node ; does li#ewise,s'own wit' 'eavy arrows2 and node ; does li#ewisewit' node = ,s'own wit' bro#en arrows*wit' node = ,s'own wit' bro#en arrows*

For a$$lications suc' as Fixed Tele$'ony atelliteFor a$$lications suc' as Fixed Tele$'ony atelliteervices2 %oint-to-$oint connectivity between node 3ervices2 %oint-to-$oint connectivity between node 3and node ; can be c'an&ed on demand*and node ; can be c'an&ed on demand*


21/47

Satellite Point to Point ConnectivitySatellite Point to Point Connectivity


22/47

Satellite Point to "ultipoint ConnectivitySatellite Point to "ultipoint Connectivity

T'e $oint-to-multi$oint connectivity is illustrated inT'e $oint-to-multi$oint connectivity is illustrated inFi&ure 5*=*Fi&ure 5*=*

T'e t'ic#2 s'aded arrows re$resent t'e di&ital broadcastT'e t'ic#2 s'aded arrows re$resent t'e di&ital broadcastEoutroute from t'e 'ub to t'e remote nodes ,ot'erEoutroute from t'e 'ub to t'e remote nodes ,ot'er

acce$table terms for t'e 'ub transmitted si&nal areacce$table terms for t'e 'ub transmitted si&nal areEoutbound2 Eforward2 and Edownstream*Eoutbound2 Eforward2 and Edownstream*

It contains all 'ub-ori&inated data to be delivered to t'eIt contains all 'ub-ori&inated data to be delivered to t'eV!Ts t'rou&'out t'e networ#*V!Ts t'rou&'out t'e networ#*

T'is transmission is received by all remotes wit'in t'eT'is transmission is received by all remotes wit'in t'e

satellite foot$rint> 'owever2 it would ty$ically containsatellite foot$rint> 'owever2 it would ty$ically containaddress information t'at allows only t'e desiredaddress information t'at allows only t'e desiredremotes to select t'e information destined for t'em*remotes to select t'e information destined for t'em*

T'e t'in lines re$resent t'e Einroutes from t'eT'e t'in lines re$resent t'e Einroutes from t'eindividual remote nodes ,li#ewise2 acce$table termsindividual remote nodes ,li#ewise2 acce$table terms

include Einbound2 Ereturn2 and Eu$stream*include Einbound2 Ereturn2 and Eu$stream*


23/47

Satellite Point to "ultipoint ConnectivitySatellite Point to "ultipoint Connectivity


24/47

%ST Star &etwor'#%ST Star &etwor'#

(r&ani.ations em$loy V!Ts $rimarily as re$lacements(r&ani.ations em$loy V!Ts $rimarily as re$lacementsfor terrestrial data networ#s usin& $rivate lines in afor terrestrial data networ#s usin& $rivate lines in avariety of a$$lications2 includin& retailin&2 $ostal andvariety of a$$lications2 includin& retailin&2 $ostal and$ac#a&e delivery2 automobile sales and service2 ban#in&$ac#a&e delivery2 automobile sales and service2 ban#in&and finance2 travel and lod&in&2 and &overnmentand finance2 travel and lod&in&2 and &overnment

administration and security*administration and security* %er'a$s t'e first ma+or installation was for al-Mart2%er'a$s t'e first ma+or installation was for al-Mart2

t'e leadin& U** retailer wit' stores t'rou&'out t'et'e leadin& U** retailer wit' stores t'rou&'out t'eUnited tates and ot'er locations around t'e world*United tates and ot'er locations around t'e world*

Today2 t'ere are more t'an :?62666 two-way V!TsToday2 t'ere are more t'an :?62666 two-way V!Tsinstalled in t'e United tates and over @662666installed in t'e United tates and over @662666worldwide*worldwide*

"ot included is t'e consumer V!T desi&ned to $rovide"ot included is t'e consumer V!T desi&ned to $rovideInternet accessInternet access


25/47



26/47


V!T tec'nolo&y s'ould only be used as a su$$lementV!T tec'nolo&y s'ould only be used as a su$$lementto 'i&'-/uality di&ital fiber o$tic and wireless networ#sto 'i&'-/uality di&ital fiber o$tic and wireless networ#sof t'e world* In fact2 t'e best strate&y is often toof t'e world* In fact2 t'e best strate&y is often tocom$lement t'e terrestrial networ# infrastructure wit'com$lement t'e terrestrial networ# infrastructure wit'V!Ts so as to ac'ieve an o$timum and reliable mix*V!Ts so as to ac'ieve an o$timum and reliable mix*

For exam$le2 a )uro$ean com$any needin& to connectFor exam$le2 a )uro$ean com$any needin& to connectonly five domestic locations to a data center would findonly five domestic locations to a data center would findt'at conventional V!Ts may not be cost-effective*t'at conventional V!Ts may not be cost-effective*

Li#ewise2 a lar&e industrial or&ani.ation t'at needsLi#ewise2 a lar&e industrial or&ani.ation t'at needs

'i&'-ca$acity lin#s between ma+or sites is not a'i&'-ca$acity lin#s between ma+or sites is not acandidate for existin& V!Ts*candidate for existin& V!Ts*

T'is would clearly be a better a$$lication for fiber o$ticT'is would clearly be a better a$$lication for fiber o$ticlin#s2 if t'at were feasible2 or $oint-to-$oint satellitelin#s2 if t'at were feasible2 or $oint-to-$oint satellitelin#s*lin#s*


27/47


28/47

%ST Star &etwor'# pplication#%ST Star &etwor'# pplication#

Many centrali.ed com$anies build t'eir IT systemsMany centrali.ed com$anies build t'eir IT systemsaround t'e 'ost com$uter t'at is located at t'earound t'e 'ost com$uter t'at is located at t'e'ead/uarters or outsourced 'ostin& facility*'ead/uarters or outsourced 'ostin& facility*

T'is is an ideal startin& $oint for V!T networ# ado$tionT'is is an ideal startin& $oint for V!T networ# ado$tion

since it is centrali.ed*since it is centrali.ed* Table 5*= $rovides a listin& of $o$ular IT a$$licationsTable 5*= $rovides a listin& of $o$ular IT a$$lications

now $rovided over enter$rise V!T networ#s*now $rovided over enter$rise V!T networ#s*

)xam$les include8)xam$les include8

9etail Mar#etin&Aal-Mart and < Drou$9etail Mar#etin&Aal-Mart and < Drou$

!utomotiveA


29/47


30/47

%ST Star &etwor'# pplication#%ST Star &etwor'# pplication#

T'e arc'itecture of t'e ty$ical V!T star networ# isT'e arc'itecture of t'e ty$ical V!T star networ# is$rovided in Fi&ure 5*@ t'at de$icts 'ow t'e user$rovided in Fi&ure 5*@ t'at de$icts 'ow t'e userconnects com$uters2 %Cs and ot'er terminals2 %BG andconnects com$uters2 %Cs and ot'er terminals2 %BG andtele$'one systems2 and video e/ui$ment used intele$'one systems2 and video e/ui$ment used in$rivate broadcastin&*$rivate broadcastin&*

T'e 'ub of t'e star is s'own on t'e ri&'t in t'e form ofT'e 'ub of t'e star is s'own on t'e ri&'t in t'e form ofa com$lete )art' station facility wit' a relatively lar&ea com$lete )art' station facility wit' a relatively lar&eantenna ,ty$ically =*7m at Hu-band and 4m at C-band*antenna ,ty$ically =*7m at Hu-band and 4m at C-band*

T'e most common im$lementations of t'e star networ#T'e most common im$lementations of t'e star networ#

use T


31/47

%ST Star &etwor'# rcitecture%ST Star &etwor'# rcitecture


32/47

Per#onal Computer IntegrationPer#onal Computer Integrationwit te %STwit te %ST

T'e %C is t'e ideal direct user interface wit' t'e V!T inT'e %C is t'e ideal direct user interface wit' t'e V!T ina$$lications w'ere on-line information delivery isa$$lications w'ere on-line information delivery isre/uired*re/uired*

Ty$ical tele$'one networ#s 'ave a real t'rou&'$ut ofTy$ical tele$'one networ#s 'ave a real t'rou&'$ut ofabout =6 Hb$s> lower rates are common in areas w'ereabout =6 Hb$s> lower rates are common in areas w'ere

line /uality is $oor*line /uality is $oor* T'is was once ade/uate for a$$lications suc' as on-lineT'is was once ade/uate for a$$lications suc' as on-line

service connection2 dial-u$ terminal access to e-mail2service connection2 dial-u$ terminal access to e-mail2and fax*and fax*

it' t'e &rowt' of t'e orld ide eb and t'eit' t'e &rowt' of t'e orld ide eb and t'eincreasin& demand for t'e transfer of lar&e files forincreasin& demand for t'e transfer of lar&e files for&ra$'ics2 database2 and en&ineerin& a$$lications2 t'e&ra$'ics2 database2 and en&ineerin& a$$lications2 t'eanalo& tele$'one networ# ceases to be ade/uate*analo& tele$'one networ# ceases to be ade/uate*

T'e mar#et$lace is $rovided wit' V!T networ#s t'atT'e mar#et$lace is $rovided wit' V!T networ#s t'at

'ave ty$ical inbound t'rou&'$uts in t'e ran&e of 3:5'ave ty$ical inbound t'rou&'$uts in t'e ran&e of 3:5Hb s to :Mb s*Hb s to :Mb s*


33/47


!n exam$le of usin& t'e $oint-to-multi$oint feature and!n exam$le of usin& t'e $oint-to-multi$oint feature andt'e %C is s'own in Fi&ure 5*4*t'e %C is s'own in Fi&ure 5*4*

T'e data files or streams are u$lin#ed from a 'ub )art'T'e data files or streams are u$lin#ed from a 'ub )art'station at t'e ri&'t*station at t'e ri&'t*

! $ublic I% or content delivery networ# service would! $ublic I% or content delivery networ# service wouldown and o$erate t'e 'ub*own and o$erate t'e 'ub*

Information is delivered to t'e 'ub over bac#'aulInformation is delivered to t'e 'ub over bac#'aulcircuits from one or more servers or ot'er informationcircuits from one or more servers or ot'er informationsources ,e*&*2 a stoc# mar#et tic#er*sources ,e*&*2 a stoc# mar#et tic#er*

ubscribers $urc'ase and install a receive-only V!T2ubscribers $urc'ase and install a receive-only V!T2w'ic' need only receive t'e 'i&'-s$eed forward lin#w'ic' need only receive t'e 'i&'-s$eed forward lin#broadcast from t'e 'ub*broadcast from t'e 'ub*


34/47



35/47

Operation of "ultiple cce##Operation of "ultiple cce##Protocol# in %ST#Protocol# in %ST#

T'e inbound c'annel is s'ared by multi$leT'e inbound c'annel is s'ared by multi$leV!Ts t'at transmit t'eir data in bursts*V!Ts t'at transmit t'eir data in bursts*

Two basic multi$le access met'ods are usedTwo basic multi$le access met'ods are used

for t'is $ur$ose8for t'is $ur$ose8 T


36/47

Operation of "ultiple cce##Operation of "ultiple cce##Protocol# TD"Protocol# TD"

!n exam$le of a T


37/47

Operation of "ultiple cce##Operation of "ultiple cce##Protocol# TD"Protocol# TD"


38/47

Operation of "ultiple cce##Operation of "ultiple cce##Protocol# LO*Protocol# LO*

!not'er a$$roac' for se$aratin& t'e inbound c'annel!not'er a$$roac' for se$aratin& t'e inbound c'anneltransmissions in time is t'e !L(1! $rotocol*transmissions in time is t'e !L(1! $rotocol*

T'e sc'eme is sim$ler in t'at t'e transmissions areT'e sc'eme is sim$ler in t'at t'e transmissions areuncoordinated> 'owever2 t'e com$lexity occurs because t'ereuncoordinated> 'owever2 t'e com$lexity occurs because t'ereare occasional overla$s t'at result in lost communication*are occasional overla$s t'at result in lost communication*

T'is is overcome by retransmissions from t'e affected V!Ts*T'is is overcome by retransmissions from t'e affected V!Ts* For exam$le2 a slotted !L(1! c'annel wit' t'ree users isFor exam$le2 a slotted !L(1! c'annel wit' t'ree users is

s'own in Fi&ure 4*?*s'own in Fi&ure 4*?*

lottin& refers to re/uirin& t'at t'e !L(1! $ac#ets fall wit'inlottin& refers to re/uirin& t'at t'e !L(1! $ac#ets fall wit'intimed $eriods2 indicated by t'e vertical lines*timed $eriods2 indicated by t'e vertical lines*

T'e u$$er t'ree 'ori.ontal lines re$resent t'ree V!TT'e u$$er t'ree 'ori.ontal lines re$resent t'ree V!Tu$lin#s> t'e bottom timeline de$icts t'e downlin# s'owin&u$lin#s> t'e bottom timeline de$icts t'e downlin# s'owin&'ow t'e !L(1! $ac#ets a$$ear after $assin& t'rou&' t'e'ow t'e !L(1! $ac#ets a$$ear after $assin& t'rou&' t'esatellite re$eater*satellite re$eater*


39/47


)ac' V!T remains in an idle state until t'ere is data to be)ac' V!T remains in an idle state until t'ere is data to betransmitted*transmitted*

Lets assume t'at V!T 3 is t'e first to need t'e c'annel andLets assume t'at V!T 3 is t'e first to need t'e c'annel andso transmits t'e bloc# of data wit'out waitin&*so transmits t'e bloc# of data wit'out waitin&*

V!T : transmits next2 inde$endently of w'at 'a$$ens atV!T : transmits next2 inde$endently of w'at 'a$$ens at

users 3 and ;*users 3 and ;* From t'e downlin# timeline2 we see t'at V!T 3 and V!T :From t'e downlin# timeline2 we see t'at V!T 3 and V!T :

do not overla$ and 'ence &et t'rou&' in t'e clear*do not overla$ and 'ence &et t'rou&' in t'e clear*

T'e next $ac#ets from V!Ts 3 and ; 'ave reac'ed t'eT'e next $ac#ets from V!Ts 3 and ; 'ave reac'ed t'esatellite at a$$roximately t'e same time and so 'avesatellite at a$$roximately t'e same time and so 'ave

$roduced a collision*$roduced a collision* In t'e event of suc' a time overla$2 t'e si&nals +ameac'In t'e event of suc' a time overla$2 t'e si&nals +ameac'

ot'er and t'e information is lost ,indicated by t'e $resenceot'er and t'e information is lost ,indicated by t'e $resenceof a dar# bloc# in t'e downlin#*of a dar# bloc# in t'e downlin#*

"eit'er $ac#et is received at t'e 'ubAa condition t'at is"eit'er $ac#et is received at t'e 'ubAa condition t'at is

inferred by t'ese V!Ts because of non-ac#nowled&ment byinferred by t'ese V!Ts because of non-ac#nowled&ment byt'e 'ub over t'e outbound c'annel*t'e 'ub over t'e outbound c'annel*


40/47


T'e way t'at $ac#ets are ultimately transferred is t'rou&'T'e way t'at $ac#ets are ultimately transferred is t'rou&'automatic retransmissions2 as s'own at t'e ends of t'eautomatic retransmissions2 as s'own at t'e ends of t'ecurved arrows in Fi&ure 4*?*curved arrows in Fi&ure 4*?*

T'e delay between t'e ori&inal and retransmitted $ac#ets isT'e delay between t'e ori&inal and retransmitted $ac#ets isselected randomly by eac' V!T to reduce t'e $ossibility of aselected randomly by eac' V!T to reduce t'e $ossibility of a

second collision*second collision* T'e result of t'is $rotocol is t'at t'e delay is as small as itT'e result of t'is $rotocol is t'at t'e delay is as small as it

can $ossibly be for a $ac#et t'at does not ex$erience acan $ossibly be for a $ac#et t'at does not ex$erience acollision*collision*

For one t'at does2 t'e delay is len&t'y since it includes atFor one t'at does2 t'e delay is len&t'y since it includes atleast two round-tri$ delays $lus t'e delays of t'e randomleast two round-tri$ delays $lus t'e delays of t'e randomoffset as well as from $rocessin& wit'in t'e 'ub and V!T*offset as well as from $rocessin& wit'in t'e 'ub and V!T*

In an acce$table o$eratin& situation2 only 3 in 36 !L(1!In an acce$table o$eratin& situation2 only 3 in 36 !L(1!$ac#ets will ex$erience a collision*$ac#ets will ex$erience a collision*


41/47



42/47

"o$ile Satellite Service#"o$ile Satellite Service#

1istorically2 D)( satellites 'ave $rovided most of t'e M1istorically2 D)( satellites 'ave $rovided most of t'e Mca$abilities2 in terms of land2 sea2 and air*ca$abilities2 in terms of land2 sea2 and air*

T'e economy and sim$licity of a sin&le satellite alon& wit'T'e economy and sim$licity of a sin&le satellite alon& wit't'e ability to use fixed antennas on t'e &round 'ave allowedt'e ability to use fixed antennas on t'e &round 'ave allowedD)( to become most suited for t'ese a$$lications*D)( to become most suited for t'ese a$$lications*

In addition to t'e &lobal ca$ability of Inmarsat2 a number ofIn addition to t'e &lobal ca$ability of Inmarsat2 a number ofD)(M networ#s ca$able of servin& 'and'eld satelliteD)(M networ#s ca$able of servin& 'and'eld satellitetele$'ones are in service*tele$'ones are in service*

T'e ma+or benefit of t'e lower orbits is reduced time delayT'e ma+or benefit of t'e lower orbits is reduced time delayfor voice services*for voice services*

T'is factor is very im$ortant in terrestrial tele$'oneT'is factor is very im$ortant in terrestrial tele$'onenetwor#s2 $articularly wit' 'i&'-/uality transmission asnetwor#s2 $articularly wit' 'i&'-/uality transmission as$rovided t'rou&' fiber o$tic tec'nolo&y*$rovided t'rou&' fiber o$tic tec'nolo&y*

Table 33*; $rovides a summary of #ey attributes of L)(2 M)(Table 33*; $rovides a summary of #ey attributes of L)(2 M)(and D)( atellites*and D)( atellites*


43/47



44/47



45/47


+igure ,,.- #election of u#er terminal euipment for u#e wit "o$ile Satellite Service#


46/47



47/47

0101

JJJJJJJJ

Satellite Communication - 7

Documents

Transcript of Satellite Communication - 7