一个创新的计划,增加连接和ZigBee网络生活

JSupercomput(2013)65:136–153DOI10.1007/s11227-011-0696-zAninnovativeschemeforincreasingconnectivityandlifeofZigBeenetworksChia-MingWu·Ruay-ShiungChang·Pu-ILee·Jei-HsiangYenPublishedonline:30September2011©SpringerScience+BusinessMedia,LLC2011AbstractZigBeenetworksbasedontheIEEE802.15.4standardaredesignedforwirelesssensorandcontrolnetworkswithlow-cost,low-powerconsumption,andlow-datarate.TojoininaZigBeenetworkwiththetreetopology,thehardwarerequirementofadeviceissimpleandlowthreshold.However,adevicemaybecomeanisolatednodeduetoconstraintsofconfigurationparametersintheZigBeenetwork.Todecreaseisolatednodes,weproposeanapproachcalledEnhancedConnectivitySchemefortheZigBeenetwork.Thisschemecanefficientlyreconstructpartsofthenetworktoletmoredevicesjoin,andhenceincreasethejoinratio.ExperimentalresultsshowthatourmethodcanefficientlyimprovetheconnectivityofZigBeenetworks.Inthispaper,wealsoproposeaswappingmethodtoextendthelifeoftheZigBeenetwork.Theobjectiveofswappingistobalancetheenergyconsumptionofthenodes.ExperimentalresultsshowthattheswappingschemecanincreasethelifeofthenetworkcomparedtotheZigBeestandardoperationby50%.WeprovideaninnovativesolutionforincreasingconnectivityandlifeofthenetworktoZigBeedesigns.KeywordsZigBee·Wirelesssensornetworks·Isolatednode·ConnectivityC.-M.Wu()·R.-S.Chang·P.-I.Lee·J.-H.YenDept.ofComputerScienceandInformationEngineering,NationalDongHwaUniversity,Hualien,Taiwan,ROCe-mail:[e-mail]orincreasingconnectivityandlifeofZigBee137e-mail:[e-mail]-mail:[e-mail]-mail:[e-mail]1IntroductionAwirelesssensornetworkisanetworkusedtoconnectsensorswithlimitedhardwarecapabilities[3,4].ZigBee[11,17,18]basedontheIEEE802.15.4standard[8]isdesignedforlow-cost,low-rate,andlow-powerwirelesssensorandcontrolnetworks.BecausethehardwarerequirementofadeviceforjoininginZigBeeislow,ZigBeeiswidelyappliedinvariousfieldssuchashomeautomation,buildingautomation,andindustrialautomation[16].Threetypesofdevices,ZigBeeCoordinator(ZC),ZigBeeRouter(ZR),andZigBeeEndDevice(ZED)aredefinedinZigBeenetworks.TheZigBeenetworkisformedbyoneZCandmultipleZRs.OnlyZCcaninitiateaZigBeenetwork.Afterinitiating,ZCacceptsthejoinrequestfromZRorZEDtoextendtheZigBeenetwork.AjoinedZRcanalsoacceptthejoinrequestsfromZEDsorotherZRstoextendthenetwork.AdevicecanjointooneZCorZRatmost.ZigBeesupportsthreekindsofnetworktopologies:star,mesh,andtree.Inanetworkwiththestartopology,alldeviceshavetoconnecttoZC.Fortreeandmeshtopologies,devicesuseamultihopmannertocommunicatewitheachother.OnlyZCandZRcanforwardpackets.Figure1showsaZigBeenetworkwiththetreetopology.ManyresearchpapersaboutZigBeenetworkshavebeenpublishedinrecentyears.Mostofthemfocusonthepowerconsumption[1,15],thesensornetworkcoverage[4],thedatabroadcastapproach[5,6],andtheroutingalgorithm[9,10].Insuchresearches,theyassumethatZigBeenetworkshavegoodconnectivity.Whendevicesarerandomlydeployed,adevicemaybecomeanisolatednodethatcannotjointoanyZCorZRinaZigBeenetworkeventhoughitscommunicationrangecanreachotherjoinednodes.ThereasonthatcausesisolatednodesisthenumberofnodesconnectingtoZRorZCislimited[7].TheconnectivityofZigBeenetworksprofoundlyaffectsthecommunicationperformance.In[12],theauthorspresentamethodtoreconnectthejoinednodewhilethelinkbetweenthisjoinednodeanditsneighbornodeisbreakage.Thismethodcannotletmoreisolateddevicesjointothenetwork.In[13],theauthorsproposeamethodtoimprovetheconnectivityofZigBeenetwork.Theyapproachusestheconnectionshiftmethodtodecreasethenumberofisolateddevices.Whileajoinednodethathasnocapacitytoacceptmorenodesreceivesjoinrequestsfromisolatednodes,itcandisjoinitsshiftablechildnodestoacceptthejoinrequest.However,whilemultipleisolatednodessendthejoinrequeststoajoinednode,usingthemethodin[13]thejoined138C.-M.Wuetal.node’sselectioncannotgainthebestconnectivity.Fig.1AZigBeenetworkwiththetreetopologySwappingtwonodescannotonlyimprovetheconnectivitybutalsoextendthelifeofthenetwork.BecausetheZRcanconnectmorenodes,swappingajoinedZEDandanisolatedZRcanpotentiallydecreasethenumberofisolatednodes.SwappingajoinedZRandanisolatedZRcanalsoincreasethenumberofjoinednodesiftheisolatedZRcanconnectmorenodesthanthejoinedZR.Thus,swappingtwonodescanincreasetheconnectivityintheZigBeenetwork.TheenergyconsumptionofaninternodeZRismorethanthatofaleafZRsincetheinternodeZRhastoforwardpacketsandworkinsensing.IfaninternodeZRisshutdown,thecommunicationsofitschildrenarebroken.ItprofoundlyaffectstheconnectivityoftheZigBeenetwork.WecanswaptheinternodeZRwithaleafZRtoextendthelifeofthenetworkwhiletheenergyoftheinternodeZRisexhausted.Inthispaper,weproposeanextendedjoiningproceduretoimprovetheconnectivityoftheZigBeenetwork.WeuseanapproachcalledEnhancedConnectivitySchemetodeterminewhichnodeisselectedfromallisolatednodestodecreasethemostnumberofisolatednodes.Intheextendedjoiningprocedure,wealsouseaswappingmethodtoconnectmoredevicesintheZigBeenetwork.Furthermore,weproposeaswappingmechanismtoextendthelifeofthenetwork.Aftercalculating