OverviewoftheWIDENSArchitecture,aWirelessAdHocNetworkforPublicSafetyRa - PDF document

OverviewoftheWIDENSArchitecture,aWirelessAdHocNetworkforPublicSafetyRaymondKnopp,NavidNikaein,andChristianBonnetInstitutEur´ecom06904,SophiaAntipolis,FranceEmail:Firstname.Name@eurecom.frHerv´eAiache,VaniaConan,SandrineMassonGr´egoireGuib
,andChristopheLeMartret
Thales,ArchitectureFrameworkCentreThales,SignalProcessingandMultimediaF-92704Colombescedex,FranceEmail:Firstname.Name@fr.thalesgroup.comAbstract—ThispaperhighlightspreliminaryresultsandstatusfortheEuropeanProjectentitledWIrelessDEployableNetworkSystem(WIDENS)[1].ThepurposeofthisIndustry/Academiacollaborativeresiearcheffortistodesign,prototypeandvalidateaverticallyintegratedrapidlydeployableandscalablecommu-nicationsystemforfuturepublicsafety,emergencyanddisasterapplications.Insuchscenarios,thecommunicationsystemmustbehighlyreliabletoallowrescueteamstoworkandcollaboratequicklyandefciently.Suchoperationsarestronglydependentontheavailabilityofthecommunicationlinksbothtorescueoperatorsontheeldsandtothecentralcontrolroom.However,indisasterareas,thelinksandcentralcontrolaresubjecttofailure,leadingtoacompletecollapseofthenetwork.Toaddresstheseissues,WIDENSexploitstheadvantagesofwirelessmobileadhocnetworksinaccordancewithpublicsafetyusagescenarios.Theprojectpartners1aredesigningthesystemandsoftwarearchitectures,andprototypingtheradiofrequency,airinterface,network,andapplicationlevelhardwareandsoftware.Theprojectsupportstheon-goingEuropeaninvolvementinthejointETSI/TIAstandardizationinitiativeMESA(MobileBroadbandforEmergencyandSafetyApplications).Thedesignandprototypedevelopmentswillcontributetothedevelopmentoffuturebroadbandprivatemobilecommunicationsystems.I.INTRODUCTIONTOTHEWIDENSNETWORKThegoalsofWIDENSprojectarethefollowing:(i)intermsoftechnology:toinventanddemonstratesolutionsthatmakerapidlydeployableandscalablecommunicationsystemforfuturepublicsafetyeffective,and(ii)intermsofmarket:toproposeadhochotspotsasaccessnetworkstoexistingPrivateMobileRadiosystemssuchasTETRAandTERTRAPOL(iii)intermsofstandardizationactivities:tosupporteuropeanparticipationtotheon-goingactivitiesoftheMESAgroup.PotentialusersfortheWIDENScommunicationsystemarethepublicsafetyprofessionalsfromdifferentorganizations:reservices,police,emergencymedicalservices,andotherparticipatingauthorities,e.g.environmentalormilitaryex-perts.Thepublicsafetyforces,whentheymobilizeresourcesforanintervention,areorganizedinsmallgroupsofseveralunitsinteractingamongeachother.Thedetailedorganizationalstructurevariesbetweendifferentpublicsafetyorganizations,butthemaincharacteristicsarethesame,thestructureisessentiallyhierarchical:atthebottomofthehierarchy,eachrescueunitmemberhasdirectconnectionwithhisownrescue1Seewww.widens.orgunitmembersandwiththeunitleader.Theunitleaderisabletocommunicatewiththemembersinhisunitandisresponsibleforreportingandreceivinginstructionsfromtherescueteamleader.Therescueteamleaderisresponsibleofmanagingthedifferentrescueunitleadersintheeld.Thepurposeofthesystemistoofferacommoncommunicationchannelthroughawirelessadhocnetworktoallactorsinanemergencysituationintheeldofoperationatthetimeofintervention,foreachorganizationandacrossorganizations.Inemergencysituations,thepublicsafetyforcesmayfacedifferentscenarios.Thesescenarios,dependingonthetypeandsizeofthedisaster,canbeclassiedinfourmajorgroupsfromthetopologicalpointofview:(i)Concentration:Emergencyservicesconcentratedinapoint(e.g.abuscrash);(ii)Front:Emergencyservicesworkingalongafrontline(e.g.reinaforest,oods);(iii)Ring:Emergencyservicesworkingaround(butnotinside)aplace(e.g.urbanres,bankrobberies,bombdeactivation);(iv)RandomDistribution:Sparse/verywidedisastersinawidearea(e.g.anearthquake,aterroristicattack).ThedesignoftheWIDENSsystemtakesadvantageofthespecicityoftheorganizationalandoperationalconstraintsofthepublicsafetyemergencyanddisasterreliefapplications.Theclusteredandhierarchicalnatureofcommunicationsaretakenintoaccountindesigningthearchitectureandcross-layeroptimizationsallowingefcientoperationoftheadhocsystem.Therestoftheproposalisorganizedasfollows.SectionIIhighlightsthearchitectureprincipleforthecross-layeropti-mizationofthesystem.SectionIIIsummarizestheMAC/PHYlayerdesign.SectionIVpresentsthenetworklayerdesign.FinallysectionVdrawsconcludingremarksandhighlightssomefuturework.II.ARCHITECTURE:INTEROPERABILITY,CROSS-LAYERING,ANDRECONFIGURABILITYFig.1showsthearchitectureofWIDENSaimingtoachievethreemainobjectivesofinteroperability,cross-layering,andrecongurabilityatthesametime.First,itconformswiththeinter-layerindependancyandpeer-to-peerprinciplesandhenceprovidesinteroperabilitybetweendifferentstandardsateach layer.Thisprovidesamodular,upgradeable,andcompatiblearchitecture.MSystem ParametersState Info &State Info &ParametersProtcols' AutoCross LayerProtocol StackAt deploymentOn OperationNetworkTransportApplicationParametersState Info &Fig.1.WIDENSarchitectureaimingatinteroperability,cross-layering,andrecon®gurabilitySecond,itextendscross-layeringtoallprotocolstacksthroughstateinformationandparametermappingbetweenadjacentlayers.Suchamappingisbeyondtheregularlayeredbehaviorinthesensethatifthelocaladaptationisinsufcienttorespondefcientlytothelocalperformancedegradation,stateinformationandparametersaremappedtotheadjacentlayerforamoregeneral/specicresponse.Thistriggerstheadaptationatthisadjacentlayer.Thus,themappingmightbefurthercross-layeredtothenextadjacentlayeriftheadaptationisinsufcient,avoidingloopsandunnecessaryorunintendedcross-layering[2].Besides,theinteractionsbe-tweennon-adjacentlayersiscontrolledviatheadjacentlayers,allowingcross-layeroptimizationwithoutaffectingtheregularfunctionalityofthelayerwhoseresponseinnotsufcient.Forexample,consideraweaklinkscenario.TheMAC/PHYcanrespondtoweakconnectivitybyincreasingthetransmitpowerorbyerrorcorrectioncoding.Thiswillcorrectthevariationsinconnectivitydueto,forexample,multipathatfading.However,ifthisresponseisnotsufcient,forwardingmechanismatthenetworklayercanreroutetrafcthroughhighqualitylinks.Ifreroutingisnotpossible,thetransportlayercandelaypackettransmissionsuntileitheralternateroutesbecomeavailableorlinkqualitybecomesgood.Tosumup,eachlayeroftheprotocolstackrespondstolocalvariationsandstateinformationfromtheotherlayers[3].Finally,itrapidlyreconguresthenetworkfunctionstothesystemconstraints(e.g.radiofrequency,bandwidth,au-thorizedtransmissionpower)andnetworkandapplicationcharacteristics(e.g.trafcandmobilitypattern)atthetimeofdeployment.Theadvantageoftherecongurableprotocolsisthatnosinglesystemisefcientforallemergencysituationsduetothehugevariabilityinterrains,trafcscenarios,andmobilitypatterns.Forinstance,thedesignoftheairinterfacecanberecongurablewithrespecttoPHYandMACparame-ters(e.g.frame/slotdurations,modulationformats,FFTsizes,preamblelengths,etc.)aswellasalgorithmsdesignedforspecicpropagationortrafcconditions(multiple-accessandchannelcodingandsynchronizationstrategies,smartantennaprocessing,schedulingalgorithms).WeareawareofoneexistingarchitecturenamedMo-bileManthatdealswiththecross-layerdesignthroughdatasharing[4].SimilartoMobileManreferencearchitecture,theWIDENSarchitecturesatisesthelayer-separationprinciple.Incontrast,WIDENSdoescross-layeringviamappingonlybetweenadjacentlayers,whileMobileMandoesthroughso-callednetworkstatusthatfunctionsasarepositoryfordatasharingamongalllayers.WIDENSalsointroducesrecong-urabledesignparameterschosenatthetimeofdeploymenttoadjustthefunctionalityoftheprotocolstacktodifferentsystemconstraintsandenvironments.III.MAC/PHYLAYERDESIGNA.RadioFrequencyEquipmentWIDENSradioequipmentshouldbetunableoverawidebandwidthinordertoaccommodateregionaldifferencesinspectralallocation.Theinitialprototypewilltarget5MHzchannelsfrom4000-5500GHz,whichincludesthespectrumliberatedforbroadbandpublicsafetysystemsintheNorthAmerica(4940-4950MHz).Thisspectralagilityiscoherentwiththerecongurabilityfeatureofthesystemarchitecture.TransceiverswillbeMIMO(multiple-inputmultiple-output)capable[5]andwillsupporttransmitpowersofupto27dBm(5MHzchannels)perantennaelement.B.MAC/PHYCo-DesignArchitectureTheimportanceoftheco-designofMACandPHYlayerwithcross-layeringinmindistakenintoaccountinWIDENSasinsomeofthelateststandardizationissuessuchasIEEE802.11e,3GPP,HiperLAN/2.Forexample,thedatalinkcontrol(DLC)andPHYlayerofBroadbandRadioAccessNetwork(BRAN)HiperLAN/2havebeendesignedforhighthroughput,lowlatency,andQoSsupport[6].TheWIDENSnetworkaimsatprovidinghighbitratewirelesslinksusingOFDM(A)modulation(802.16xproposals[7],3GPPHSDPA[8])withhigh-orderQAMconstellations.Thetimingandfrequencysynchronizationwillbeachievedwithspeciallydesignedsynchronizationsequencesperiod-icallybroadcastedbythebestlocatedTerminodeswithintheclusterthatactsascoordinators,whichpermitaccuratesimultaneoustimeoffsetestimationandcarrierfrequencytracking.Terminodeswilllockintimeandfrequencyonaframe-by-framebasistothesesynchronizationsignals(seeFig.2).Moreover,thesignalswillbedesignedtoallowforadjacentclusterstosynchronizetoeachotherbyensuringtime/frequencytrackingoverlongerdistancesthanthosecon-sideredfortransmittingdata.Thechannelaccessishybridinthesensethatitoperatesbothonrandomandscheduledaccess.Thelimitbetweenrandomandscheduledaccessisdynamicallyadjustedbythecoordinatortomaximizeresourceutilizationwithrespecttotheoveralltrafccharacteristicswithinacluster.ScheduledaccesscanbeseenastransmissionopportunitiesforTermin-odesgivenbythecoordinatorinthebroadcastchannel(BCH).TrafcdoesnotnecessarilypassthroughthecoordinatorsinceroutingisdeterminedbytheNetworkLayer.Terminodesareatlibertytoscheduletheirtrafcaccordinglywiththeirtransmissionopportunitiesorpotentiallyintherandom-accessphase. CTRL...DATAstream 1stream NRandom AccessOFDM(A)Slot/Carrier/Antenna MUXSchedualed AccessFrameSynchronizationOpportunistic Scheduling & Channel CodingFig.2.MAC/PHYarchitectureTheMAC/PHYlayercombinesopportunisticschedulingtechniques[9]andchannelcoding/ARQinasingleentity(seeFig.2).Thedataunitsarescheduledacrosscontentionandcontention-freeperiodaccordingtoQoSlevelsandphysicalresources(i.e.frequencies,antenna,timeslots).ThisindicatesthattheresourceallocationisdoneattheMACallowingforrapidresponsetime.TheMAC/PHYlayerismultiuser/streamcapable(incontrasttoIEEE802.11legacy)duetotime-frequencyslottednatureofthechannelandtheOFDM(A)characteristics.IV.NETWORKLAYERDESIGNTheNetworkLayerfunctionalitiesidentiedforWIDENSaregatheredintothreedifferentplanes,whichcorrespondtothreedifferenttimescales:theforwarding,controlandman-agementplanes.Forminganad-hocnetwork,theWIDENSTerminodesactbothasroutersandasend-devicesandtakeadvantageofthecross-layeringdesigntooptimizecommuni-cationchannelusage.Theforwardingplaneisimplementedinkernelspace,whilecontrolandmanagementplanesareimplementedasprocessesinuserspace[10].A.ForwardingplaneTheforwardingplaneimplementstimecriticalfunctionsandincreasesitsefciencybymappingpropertiesbetweenNetworkLayerandMAC/PHYLayer.Thisplaneconsistsofthefollowingfunctionalities:forwardingdeterminesthenexthoptowhichapacketmustberelayed;accesscontrol,associatedwithsecurity,checksifthepacketcanbeacceptedornotbythesystem;packetclassicationlterspacketsinordertoperformdifferentiatedQoS;policingchecksthatthecurrentowtrafccharacteristicsareinaccordancewiththedeclaredtrafcdescriptors;torespondtoQoSrequirements,schedulingcanbeperformedattheNetworkLayerordirectlyattheMAC/PHYLayerduetocross-layeringdesign.B.ControlplaneThemanagementplanecoversthenetworkdeploymentphasebytranslatingusersrequirementsintonetworkcongu-rations.ItrepresentsthenecessaryelementstomakethelinkbetweenusersandtheWIDENSsystem.Infact,duetothemanagementfunctions,aTerminodeisnotonlyanetworkelementbutbecomesanactiveelementoftheglobalWIDENSsysteminaspecicoperatingcontext.Itisinchargeofthesettingofthecommunicationpatterns,applicationprolesandorganizationpoliciesspecictotheemergencyoperation,themanagementofkeystobeusedbysecurityfunctions,theaddressingcongurationandthelogstorage.C.ManagementplaneThemaintaskofthecontrolplaneistoestablishandtocontrolcommunicationsbetweenMAC/PHYclusters,sinceintra-clustercommunicationsareessentiallymanagedbytheMAC/PHYcoordinator.Itinteractswithapplicationsandwiththemanagementplaneandmodiesdynamicallythetablesandparametersusedbytheforwardingplane.Controlfunc-tionsinvolvecoordinationbetweenthenodesofthenetwork,organizedinclustersbytheMAC/PHYLayer.Itusessignalingforinformationexchange.Routingisthefunctionthatallowseachnodetobeabletodeterminethenexthopnodetowhichapacketmustberelayedtoreachagivendestination.Toguaranteeavailabilityofnetworkresourcesforaspecicow,reservationisperformedthroughsignalingandadmissioncontrol.Securityfunctionsprovideintegrityandauthenticationoftheterminodesimpliedontheroutingprotocol,topreventbasicattacksontheroutingprotocollikeblackholeattackoraroutingtableoverow.V.CONCLUSIONTheWIDENSprojectaimsatdesigning,prototyping,andvalidatingarapidlydeployableandscalablecommunica-tionsystemthroughawirelessmobileadhocnetworkforfuturepublicsafety,emergency,anddisasterapplications.TheWIDENSarchitectureextendsthestandardlayered-independancytosupportcross-layeringonoperation,andrecongurabilityatthedeployment.Theprojecthaspro-ducedthesystemspecicationsforawirelessmobileadhoccommunicationsystemforpublicsafetyapplications.Thesespecicationswerepresentedaboveandrelyonacross-layeroptimizationprinciple.Thenextstepintheprojectistovalidatethedesign.Simulationsandmodelsofvariouscommunicationpatternswillbecarriedout.AprototypewillbeimplementedusinganextensiontoEurecom'sSoftwareRadioPlatform,2andthecodewillbedevelopedundertheGNUgeneralpubliclicenseandreleasedinthepublicdomain.AfullRFdemonstratorwillbesetupinthecourseofyear2005.ACKNOWLEDGMENTTheWIDENSprojectisanIndustry/Academiacollabora-tiveprojectfundedinpartbytheEuropeanCommission'sInformationSocietyTechnology6thFrameworkProgramme.ItstartedinFebruary2004andisplannedtoendinJan-uary2006.TheprojectpartnersareThalesCommunications(France),InstitutEur´ecom(France),EADSTelecommunica-tions(France),UniversityofAntwerp(Belgium),Multitel(Bel-gium),TechnicalUniversityofCatalunia(Spain),TelefonicaI+D(Spain),HelsinkiUniversityofTechnology(Finland).Formoreinformationvisittheprojectwebsitewww.widens.org.2Seewww.wireless3G4free.com REFERENCES[1]WIDENSWG,“Wirelessdeployablenetworksystem(WIDENS),”2004,projectWidens,DeliverableD2.2.[2]V.KawadiaandP.R.Kumar,“Acautionaryperspectiveoncrosslayerdesign,”IEEEWirelessCommunicationMagazine,2003.[3]A.J.GoldsmithandS.B.Wicker,“Designchallengesforenergy-constrainedadhocwirelessnetworks,”IEEEWirelessCommunications,2002.[4]M.Conti,G.Maselli,G.Turi,andS.Giordano,“Cross-layeringinmobileadhocnetworkdesign,”IEEEComputerspecialissueonAdHocNetworks,2004.[5]D.Gerbert,M.Sha®,D.-S.Shiu,P.J.Smith,andA.Naguib,“Fromtheorytopractice:AnoverviewofMIMOspace-timecodedwirelesssystems,”IEEEJournalOnSelectedAreasInCommunications,2003.[6]A.Doufexi,S.Armour,P.Karlsson,A.Nix,andD.Bull,“AcomparisonoftheHIPER-LAN/2andIEEE802.11awirelesslanstandards,”IEEECommunicationMagazine,2002.[7]C.Eklund,R.B.Marks,K.L.Stanwood,andS.Wang,“IEEEstandard802.16:Atechnicaloverviewofthewirelessmanairinterfaceforbroadbandwirelessaccess,”IEEECommunicationMagazine,2002.[8]3GPPTR25.89,AnalysisofOFDMforUTRANenhancements,down-loadfromwww.3gpp.org.[9]P.Viswanath,D.Tse,andR.Laroia,“Opportunisticbeamformingusingdumbantenna,”IEEETransactionsofInformationTheory,2002.[10]E.M.RoyerandC.E.Perkins,“AnimplementationstudyoftheAODVroutingprotocol,”inIEEEWirelessCommunicationsandNetworkingConference,2000.