简介：Heterogeneouscellularnetworksimprovethespectrumefficiencyandcoverageofwirelesscommunicationnetworksbydeployinglowpowerbasestation(BS)overlappingtheconventionalmacrocell.ButduetothedisparitybetweenthetransmitpowersofthemacroBSandthelowpowerBS,cellassociationstrategydevelopedfortheconventionalhomogeneousnetworksmayleadtoahighlyunbalancedtrafficloadingwithmostofthetrafficconcentratedonthemacroBS.Inthispaper,weproposeaload-balancecellassociationschemeforheterogeneouscellularnetworkaimingtomaximizethenetworkcapacity.Byrelaxingtheassociationconstraints,wecangettheupperboundofoptimalsolutionandconverttheprimalproblemintoaconvexoptimizationproblem.FurthermoreweproposeaLagrangemultipliersbaseddistributedalgorithmbyusingLagrangedualtheorytosolvetheconvexoptimization,whichconvergestoanoptimalsolutionwithatheoreticalperformanceguarantee.Withtheproposedalgorithm,mobileterminals(MTs)needtojointlyconsidertheirtraffictype,receivedsignal-to-interference-noise-ratios(SINRs)fromBSs,andtheloadofBSswhentheychooseserverBS.SimulationresultsshowthattheloadbalancebetweenmacroandpicoBSisachievedandnetworkcapacityisimprovedsignificantlybyourproposedcellassociationalgorithm.

简介：Self-configurationofphysicalcellidentity(PCI)isakeyfeatureforthelongtermevolutionadvanced(LTE-A)network.ThePCIisusedtoidentifythedifferentcellsinthesystem,becominganessentialcellconfigurationparameter.ConsideringtheuncoordinateddeploymentsoftheevolvedNodeB(eNodeB)andthelimitednumberofPCI,thePCIassignmentforcellswouldbequitecomplex.ThispaperpresentsandputsforwardagraphtheorybasedcentralizedPCIself-configurationscheme(GT-PCIS).ThePCIself-configurationproblemismappedtothewell-knownminimumspanningtree(MST)probleminordertooptimizethePCIreusedistanceanddecreasethemultiplexinginterferencethroughouttheentirenetwork.TheproposalprovidesagreedysearchtomakethelocallyoptimalselectionofPCIateachstage,andtoachieveaglobaloptimum.Todemonstratethealgorithmvalidity,performancesofGT-PCISandmanualconfigurationareevaluated.SimulationresultsshowthattheproposedGT-PCISoutperformsotherconfigurationalgorithmsevenundertheconditionofseverePCIdeficiency.

简介：Multi-cellmulti-usermultiple-inputmultiple-output(MC-MU-MIMO)isapromisingtechniquetoeliminateinter-userinterferenceandinter-cellcochannelinterferenceinwirelesstelecommunicationsystems.AsthelargenumberofusersinthesystemandthelimitednumberofsimultaneouslysupportableuserswithMC-MU-MIMO,itisnecessarytoselectasubsetofuserstomaximizethetotalthroughput.However,thefullycentralizeduserselectionalgorithmsusedinsinglecellsystem,whichwillincurhighcomplexityandbackhaulloadinmulti-cellcooperativeprocessing(MCP)systems,arenotsuitabletoMC-MU-MIMOsystems.ThisarticlepresentsatwocascadeduserselectionmethodforMCPsystemswithmulti-cellblockdiagonalization.Inthispaper,alocaloptimalsubsetofusers,whichcanmaximizethelocalsumcapacity,isfirstchosenbythegreedymethodineverycooperativebasestationinparallel.Then,allthecooperativebasestationsreporttheirlocaloptimaluserstothecentralunit(CU).Finally,theglobaloptimalusers,whichcanmaximizetheglobalsumcapacityofMCPsystems,areselectedfromtheaggregatedlocaloptimalusersattheCU.Thesimulationresultsshowthattheproposedmethodperformscloselytotheoptimalandcentralizedalgorithm.Meanwhile,thecomplexityandbackhaulloadarereduceddramatically.

简介：Inwirelesscellularnetworks,theinterferencealignment(IA)isapromisingtechniqueforinterferencemanagement.AnewIAschemefordownlinkcellularnetworkwithmulti-cellandmulti-userwasproposed.Intheproposedscheme,theinterferenceinthenetworksisdividedintointer-cellinterference(ICI)amongcellsandinter-userinterference(IUI)ineachcell.TheICIisalignedontoamulti-dimensionalsubspacebymultiplyingtheICIalignmentprecodingmatrixwhichisdesignedbythesingularvaluedecomposition(SVD)schemeatthebasestation(BS)side.ThealignedICIiseliminatedbytimingtheinterferencesuppressionmatrixwhichisdesignedbyzero-forcing(ZF)schemeattheuserequipment(UE)side.Meanwhile,theIUIisalignedbymultiplyingtheIUIalignmentprecodingmatrixwhichisdesignedbasedonNashbargainingsolution(NBS)ingametheory.TheNBSissolvedbytheparticleswarmoptimization(PSO)method.Simulationsshowthat,comparedwiththetraditionalZFIAscheme,theproposedschemecanobtainhigherdatarateandguaranteethedataratefairnessofUEswithlittleadditionalcomplexity.

简介：Coordinatedmulti-pointtransmission/reception(CoMP)wasproposedcurrentlyasaneffectivetechnologytoimprovecell-edgethroughputinnext-generationwirelesssystems.Mostoftheexistingworkdiscussedclusteringmethodsmostlytomaximizetheedgeuserthroughputwhileneglectingtheproblemofenergyefficiency,suchasthosealgorithmclusteringbasestations(BSs)ofbetterchannelconditionandBSsofworsechannelconditiontogether.Inaddition,BSsusuallyincreasethetransmitpowertoachievehigherthroughputwithoutanyconsideringofinterferencecausedtootherusers,thatmayresultinenergywaste.TheauthorsfocusonthethroughputmaximizingproblemwhilefullyconsideringenergysavingprobleminCoMPsystems.Acoefficientisdefinedtodescribethefitnessofclusters.Thenasub-carrierallocationalgorithmwithclusteringmethodisputforwardforCoMPdownlink,whichcansavethetransmitpowerofBSandincreasethethroughput.Furthermoreapowerallocationschemeisproposedbasedonnon-cooperationgame;inwhichthetransmitpowerisdecreasedbyBSsgenerallytoreachtheNashequation(NE).Simulationshowsthattheproposedsub-carrierallocationschemeandpowerallocationalgorithmarebetterthantheexistingonesonusers’throughputwhileconsumesmuchlessenergy.