N92-24121 MSAT Network Architecture
N92-24121MSAT Network ArchitectureN.G.Daviesand B. SkerryTelesat Mobile Inc.P.O. Box 7800 Ottawa, OntarioK1L 8E4, CanadaPhone: (613) 746-5601Fax: (613) 746-2277ABSTRACTTelesatMobileInc. will provideMobileSatelliteServices(MSS) in Canadastartingin1993 using a geostationaryMSAT satellite. Thecommunicationssystem,whichis beingdevelopedin close cooperationwith the AmericanMobile Satellite Corporation,will support mobilevoice and data services using circuit switched andpacket switched facilities with interconnectiontothe public switched telephone network and privatenetworks.Controlof the satellitenetworkwill residein aNetworkControl System (NCS) which is beingdesignedto be extremelyflexible to provide forthe operationof the systeminitiallywith onemulti-beamsatellite, but with the capability to addadditionalsatelliteswhich may have other beamconfigurations.The architectureof the NCS isdescribed.The signalling system must be capableof supportingthe protocolsfor the assignmentofclrcmtsfor mobile public telephoneand privatenetworkcalls as well as identifyingpacket datanetworks.Thestructureof a straw-mansignallingsystem is discussed.INTRODUCTIONTelesat Mobile Inc. (TMI), which is authorizedto providemobilesatelliteservices(MSS)inCanada, will launch a dedicatedMSAT satellite inlate 1993 to providemobile telephone,mobileradio and mobile data services to customersonthe move in any part of Canada.The AmericanMobileSatelliteCorp. (AMSC),the licensedMSS operatorin the U.S.A.,will procureasimilarsatellite.The satellitesof the twoorganizationswill provide mutual Ottawa,is cooperatingcloselywith AMSC to define andto procure the necessarysatellitesand rway with satellitesupplierswith theobjectiveto enter into a contractin the secondquarter of 1990. The design and procurementofgroundsegmentequipmentwill proceedinparallel.The satellites and the ground system areto be ready for full operationby 1994.This paper describesthe baselineplanningofthe infrastructurefor the groundsegment.Throughclosecooperationwith AMSC,it isplannedthata commoncommunicationsinfrastructurebe designed,such that customerswill be able use their mobile terminalsanywherein NorthAmericaand will have a choiceofsuppliersfor mobileMSATterminals.SERVICEREQUIREMENTSTMI estimates the potential demand for MSS at300,000to 450,000mobile terminalsin Canadaby the year 2000. Studies of the requirementsforthe mobiledataservicesindicatethattherequirementsfor mobiledata terminalscouldreach50%to 60%of the totaldemand.Assumptionsregardingthis marketpenetrationrate indicatethat TMrssystem shouldsupport75,000 to 130,000 mobile voice terminalsby theyear 2000.In comparison,it is anticipatedthatthe marketin the U.S.A.could be three to tentimes greater.The penetrationof themarketwill dependcriticallyupon the cost of the mobile terminalsand the charge for air time, which should not betoo much greater than the equivalentcosts andchargesfor cellularservices.The MSATt990PRECEDINGPAGEBLANKNOTFILMED311
communicationsnetworkmust be designedtoprovideas muchsatellitecircuitcapacityaspossiblewith a givensatelliteusing mobileterminalsthat are cheap,very reliableand areappropriateto the land,sea and air mobileenvironments.The network design should permitmany servicesto be providedthroughmobiletransceivers which are manufacturedto a commonstandard.To aid the designof the communicationsnetwork, the service requirementsin Canada havebeenaggregatedintothe followingfourcategories.MobileRadioService(MRS)- a circuitswitched voice and data private network service.MobileTelephoneService (MTS) - a ionto the public Service(MDS)- a packetdata servicewith interconnectiontoand publicAeronauticaldata networks.Services- servicescompatiblewith internationalstandardssatellite communicationswith aircraft.whicharefor mobileThe first threecategoriesof servicewillsupport land and marine mobile services as wellas aeronauticalservicesto privateand smallcommercialaircraft. A separate category has beendefined for the provisionof aeronauticalmobilesatelliteservicesto large commercialaircraftwhich will most likely adhere to internationalstandardswhich are defined by the InternationalCivil AviationOrganization(ICAO).Othercategoriesmay be added as experienceis gained.TIIEBASELINESYSTEMTheMSATsystemwill use the L-bandfrequencies1530.0- 1559.0 MHz onwith mobileearthterminals(METs).The service area is the whole of NorthAmericaand the islandsof PuertoRico andHawaii with an option for coverageof alflight informationregions.Thiscoveragehas been definedfor the satellitesofboth systemsin order that in-orbitback-upofeach systemcan be provided.The baselinedesignfor the first generationsystem[1] hasenvisagedfive to nine beams with re-use of thelimited frequencyspectrumup to 1.3 times. Kuband frequenciesin the 11/13 GHz allotmentbands, in a single continentalbeam, will be usedfor feeder-linksto trLxed feeder-linkearth municationstransponderwill relay signalsbetweenKu-bandfeeder-linkearth stations ill not constrainthe choiceofcommunicationssignals.The baselinesystemdesignis for FDMA/SCPCmultipleaccessnarrow-bandwidthSCPC channels,nominally5kHz in bandwidth.The conceptualdesign of thesatellite transponderhas considerableflexibility toreallocatepower and bandwidthto the differentbeams or service areas of the system.A wide variety of mobile terminal types will beable to operate with the MSAT satellite.Whilethe detailed parametersof many of these terminalsare not yet firmly established,the xtensivelyexplored.It is anticipatedthat theseterminalswill have an antenna gain of 10 to 13dBic (circularlypolarized)and a correspondingG/T of -15 to -12 dB/K.MET EIRP will bebelow 16 dBW.Both analogand digitalformsof speechmodulationare being considered.Amplitudecompandedsingle sideband (ACSSB) modulationis assessedto be a veryruggedformofmodulationfor use under the severe multipath andblockinganticipatedin thelandmobileenvironment.4.8 kbps digital speech with trelliscodedmodulationis alsobecomingveryattractive.The latter form of modulationmaypermit satisfactoryoperationat lower values ofC/No, permittingmore channelsto be assignedthrougha givensatellite,but has a sharperthresholdand hence may not be so satisfactoryina highly shadowed environment.The range ofbaseline L-bandtypes of speech2,000assignablesupport100,000the pacity of thesatellite transponderand the twomodulationis some 1,000 tovoicechannelswhichcanto 200,000METs for voice ordata traffic [2].SatelliteConference,Ottawa,t990
PARTITIONED BY TMI NOC.:PARTITIONED BY AMSC NOCTMI:UTUREy\CONTROL(i IJAMSC NETWORK OPERATIONSCENTRE1.ISYSTEMSl LSYSTEMS IYSTEMSJGeneralArchitectureof a SystemARCHITECTUREThe generalarchitectureof the systemstoprovideMSS in North Americais illustratedinFigure 1. The satellitesowned respectivelybyTMI and AMSC are located at several ovidedthroughany of these satellites,or aportion of a satellite, is managedwithin a ControlGroup, to be describedin more detail later. Forbusinessreasonsor for networkrestoralin theevent of satellitefailure,capacityon the twocentral satellitesmay be allocatedto both a TMIand an AMSC Control Group.A TMI and a AMSCNetworkOperationsCentre will manage and control all the resourcesInternationalMobile1,,IThe bandwidthand poweravailablein asatellite transponderwill be subdividedinto oneway channelsof variousbandwidthsand powerlevels.Generally,forwardand returnlinkchannelswill be pairedto supporttwo-waycommunication.A symmetricalchannelpairforms a circuit.Pairings may be asymmetricforprovisioningof asymmetricservicessuch aspacket switcheddata and to support signalling.Circuits may be used for DEMANDPERIODorfor FULLPERIODcircuitswitchedservice.DEMANDPERIOD circuits are used on a call-bycall, as needed,basis;FULL PERIODcircuitsare devoted to a long term particularuse.NETWORKTMI NETWORK OPERATIONS CENTRElfT ,ER ILSYSTEMSIFigureGROUPSatelliteConference,Ottawa,to ProvideMSS in NorthAmericaof the respectivesystems.A NOCwillcoordinatethe frequenciesto be used in eachbeamand willallocateblocksof satellitebandwidthand power within beams as satellitecircuitsto a ControlGroup.The NOC alsoallocates blocks of satellite bandwidthand powerto customerssuch as the commercialaviationcommunity,who may wish to operatetheir ownmobile satellitesystem.The NOC receivesandacts upon requests for pre-emptionof frequenciesif requiredfor aeronauticalsafety services.Inrespondingto the flight safety requirements,theNOC may need to reconfigurethe frequencybands to be used by each satellitein each beamand so advise the GCs.The NOCs will carry out the administrativefunctionsassociated with managementof the totalMSS system.This includesthe registeringofMETs with their attributes,setting up conditionsso that properly authorizedMETs may access thesystem, the recordingof system usage for billingpurposesand the accumulationof networkperformancerecordsto aid in long-termsystemplanning.This architectureclearlyhas provisiontoaccommodategrowth through the addition of newsatellites (which may have a different transponderand beam configuration),and the additionofControlGroups.It alsoprovidesneededflexibilityin the allocationof resourcestodifferent Control Groups.1990313
Within this overall architecture,the provisionof DEMANDPERIOD circuits to and from METsis managedby a NetworkControlSystem(NCS).The structureof the NCS is showndiagrammaticallyin Figure 2. The elements of aNCS are a NetworkOperationsCentre (NOC), aNetworkControl Centre (NCC) and the portionsof the FESs and METs that are associatedwiththe signallingchannelsthroughwhichtheassignmentof circuits and other network controlfunctionsare exercised.A Group controller(GC)within the NCC assigns satellite circuits to meetcustomerrequirements.All interfaceswithin theNCS will be in accordancewith a specifiednetworkstandard.The operatorinterfaceat theMET and the terrestrialnetworkinterfaceat theFES will not be standardizedin order to maintainflexibilitycustomersto meet the needsor service providerof specific end-userorganizations.ORK.i/:;; :: :::: .:: :: ; : :OTHEI NOCs,:: /./YIIfCONTROLiiii::i ::. SYSTEMCENTREfNq lII:': : ::i!i!:! II ORO IIili:!i!i:iiii!i!:,, ,," SIGNAH/NO]",.ii Mo. iformed into pools large enoughto ensure highcircuit usage efficiency.The variouscustomernetworkswithin the NCS will use circuitsfromcircuit pools on an as-neededbasis.METslocatedwithinthe variousbeamsof thesystem access the GC through L-band signallingchannelsto requesta ntsfor aninterconnectionthrough a FES to the PSTN or toa private network.The necessaryinstructionsfrom a GC to a FES to set up a communicationschannelwith a MET are providedthrough Kuband signallingchannels.Calls betweenMETs,which are not expectedto be a large part of thetotal service, are establishedby double hoppingthrougha FES which is suitablyequippedtosupport such calls.Twoexamplesof virtualnetworkswillillustratethe applicationof these features of theNCS. For the first example,a single FES servesa group of METs to form a private network.Callconnectionsare made betweenthe METs and aPBXattachedto the FES.TheFESisprovisionedwith several voice channel units of asingle type. The interfacebetweenthe PBX andchannelunits providesthe necessaryprotocolconversion.Virtual network managerswithin theGC set up the pre-assignedrouting option for thisclosed user group.The second example involvesa virtual network configuredfor gicallylocated throughoutthe country andinterconnectedto the PSTN.Each FES isequippedwith a numberof channelunits andPSTN connectionsbased on traffic engineeringforecastsand the routingmethodselected.Avirtualnetworkmanagerwithin the GC sets upcall routing through a FES which is closest to thecalled party in the PSTN.Appropriaterouting isalso provided for calls to METs originatingfromthe PSTN.::?"::ii:!I:::I::.COMMUNICATIONS ::il!!/':TER R ES II:i II! : ii::i.:::i!i:!/I!.NEIWORK.: :::.i::::i::!. OPERATORINTERFACEFigureINTERFACE2. Architectureof the NCSBecausebandwidthand powerand limited,the availablesatelliteare valuablecircuitsareThe networkarchitectureprovidesfor theincorporationof packetswitchedservices,as aseparate network, which will likely operate usingFULL PERIODchannelsadministeredby a DataHub [3].SIGNALLINGThe signallingsystem providesmobileterminalsto accesstheexchangeof nference,a methodforNCS for theand networkOttawa,t990
managementinformationamong all the elementsof the NCS.The signallingsystem must servethe anticipatednumberof mobile terminalsandprovide the required responsetime for setting upcalls.One or more signallingchannelswill beneeded in each beam of each e and continuous control of all METs in thesystem.For this reason and because of the needfor a continuoussignal for MET antenna trackingandthe benefitsof a commonfrequencyreference,considerationis beinggiventorequiring all METs to receive a signalling channelat all times, even when a call is in progress.The strawmanconceptfor the signallingsystemdescribedheresupportsthe circuitswitchedservicesfor MSAT.The packetswitcheddata services,the MDS, operateonseparate channels.This signalling will be used toset up calls betweenan FES and a MET.Calltake-downwill be managed by the FES via someform of signallingon the traffic channelwithappropriatenotificationto the GC.The communicationschannels(FES-CandMET-C)are demand-assignedcircuitswitchedchannels.The type of traffic to be carried on thechannel will be negotiatedduring the call set-upand may includethe type of modulationto beused. Thus the same signalling infrastructurewillbe able to set up calls for ACSSB,4.8 kbpsCELP, stream data, etc.ChannelGC-IDescriptionInterstationsig. ch.from GC to an FESFES-IInterstationsig. ch.from an FES to GCTDMAGC-SOutboundsig.from GC to a MET"IDMMET-SInboundrandomaccess sig. ch. from aMET to the GCOutboundcom.ch.from an FES to a METInboundcom.ch.from a MET to an FESFES-CMET-CTableETFigureChannelConfigurationThe outboundFigure3 showsthe channelconfigurationbetweena GC, an FES, and a MET.Sixdifferentchanneltypes have been definedasshown in Table 1 [4].The interstationsignalling channels(GC-I andFES-I) will be a simplifiedform of many existingVSAT systems and will not be escriptionsThe signallingchannelsmay use A-BPSKtransmittedat 2400 sps. Rate 1/2 coding may beused thus giving an informationrate of 1200 bps.The use of higherrate block codesis beinginvestigated,especiallyfor the inbound channel(MET-S) in order to improve throughput.(MET)3. Signalling1. Channelch.Due to the nature of the signallingchannels,itis necessaryto have a fixed packetsize for theexchangeof information.Thesepacketsarereferred to as signallingunits (SU) and are 96 bitslong.This size was deemedto be adequateformost applicationsand is also the size that otherMSS operatorshave chosen [5,6].Controller(GC)Group M(FES)CharacteristicsTDMGS-Schanneluses time divisionmultiplexingand channelcould be interleavedover a one secondframe.Each frame couldhandle 12 SUs.Periodicbulletin boards wouldbe transmittedon this channelin order to tion,alternate signalling channels, etc.).The inbound signalling channel (MET-S)use SloppySlottedAloha(SSA)[7].schemepermitsthe use of small guardcouldThistimes.1990315
HoweverMETs do not necessarilycorrect timing on their first access.channelwill be able to supportsecond.have to haveThe MET-S10 slots perThe designprocesswillbe pursuedincooperationwith the AMSC with the intentionthat systems to be operated by the two companiesshould provide a fully compatibleservice.In additionto the SSA approach,variousreservationschemes are being investigatedwhichmay lead to greaterthroughput.The ratio ofinbound to outboundchannelswill depend uponwhich reservationscheme is selected.The detailed design and implementationof thesystems will be a major and exciting challenge.The connecttime is defined as the time fromwhich the MET or FES initiates a call to the timean end-to-endconnectionis establishedbetween aMET and FES. The performanceobjectivesareas follows:PerformanceObjectiveConnect Time (seconds)Degree of ShadowingNoneLight ModerateHeavyMean90%2.55.03.06.04.08.05.010.0Given one GC-S channelas describedaboveand as many inbound channelsas are necessary,it is desired to estimate how many users could besupported.The followingassumptionsare made:three outbound packets needed to set up a call; anaverage busy hour usage of 0.01 erlangs per user;and an average call duration of 60 seconds.Workingwith these averages,and ignoringqueuingproblems,this leadsto one GC-Schannelbeing able to supportor 240 calls inprogress(approximately24,000users).Thisnumber would be lower in actual practice, so thatthe queues could be minimized.The number ofinbound channelsrequired per outboundchannelwill depend upon the reservationscheme adopted,but will be in the range of one to five.REFERENCES1.Bertenyi,E. The MSATsatellite.InProceedingsof the 40thCongressof theInternationalAstronauticalFederation,Spain 9-13October 1989.2.Davies,N.G.and Roscoe,O.S.Theprovisionof mobile satellite services in Canada.To be published in Canadian Journal of Electricaland Computer turefor the MSAT Mobile Data System.To be publishedin these proceedingsSecondInternationalMobile SatelliteConference.June1990.4.CCIR.A NetworkControlSystemfor the North AmericanReport 8/531 Annex 5. 1989.and ion.Aussat l.Inmarsat, SeptemberSystem1989.Definition7.Crozier,S. Sloppy SlottedAloha.To bepublishedin theseproceedingsSecondInternationalMobile SatelliteConference.June1990.CONCLUSIONThis paper has describedthe conceptfor theground segment infrastructurethat will be neededto support the mobile voice and data services thatwill be providedby MSAT.The design of theground segment will be developedfurther during1990andprocurementofhardwarewillcommenceat the beginning of awa,t990
Phone: (613) 746-5601 Fax: (613) 746-2277 ABSTRACT Telesat Mobile Inc. will provide Mobile Satellite Services (MSS) in Canada starting in 1993 using a geostationary MSAT satellite. The communications system, which is being developed in close cooperation with the American Mobile Satellite Corporation, will support mobileCited by: 5Publish Year: 1990Author: N. G. Davies, B. Skerry
MSAT-G2 MOBILE SATELLITE RADIO The MSAT-G2 Mobile Satellite Radio is a powerful new communications tool that works where you do. Designed for use on the MSAT Network, the MSAT-G2 supports continent wide Push-to-Talk (PTT) and Voice communications. In
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The MSAT-G2 Mobile Satellite Radio is a radio transmitter and receiver. When turned on and operating, the MSAT-G2 antenna transmits and receives radio frequencies to and from a satellite orbiting the earth.
All phone numbers supported by your MSAT-G2 radio can be dialed (10 digit Canada/USA, 011-international calls, *72/90/92 call features, 611, etc) Once the phone number is dialed the user will hear a single “call initiate” tone. Following the tone, ringing will be heard and the o
The Athletic Training Program 10 A. ATP Admission Requirements 10 B. Curriculum Requirements 11 C. 3 2 BSHS Pre-Athletic Training Audit Sheet 12 D. MSAT Audit Sheet 13 E. Proposed 3 2 BSHS Pre-Athletic Training Curriculum Sequence 14 F. Stand-Alone MSAT Curriculum Sequence 15 .
What is Computer Architecture? “Computer Architecture is the science and art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals.” - WWW Computer Architecture Page An analogy to architecture of File Size: 1MBPage Count: 12Explore further(PDF) Lecture Notes on Computer Architecturewww.researchgate.netComputer Architecture - an overview ScienceDirect Topicswww.sciencedirect.comWhat is Computer Architecture? - Definition from Techopediawww.techopedia.com1. An Introduction to Computer Architecture - Designing .www.oreilly.comWhat is Computer Architecture? - University of Washingtoncourses.cs.washington.eduRecommended to you b
The Unified Architecture Framework (UAF) is an extensive update of the NATO Architecture Framework (NAF), UK Ministry of Defence Architecture Framework . Architecture Physical Data Model Data Definition Data System Model Program Function Technology Architecture Network Architecture Network PLANNER Objectives/Scope OWNER Conceptual
The American Revolution This French snuffbox pictures (left to right) Voltaire, Rousseau, and colonial states-man Benjamin Franklin. Enlightenment and Revolution641 Americans Win Independence In 1754, war erupted on the North American continent between the English and the French. As you recall, the French had also colonized parts of North America through-out the 1600s and 1700s. The conflict .
