Toward-green-and-soft-a-5G-perspective

IEEECommunicationsMagazine�February2014660163-6804/14/$25.00©2014IEEEINTRODUCTIONWiththematuringoffourthgeneration(4G)standardizationandtheongoingworldwidedeploymentof4Gcellularnetworks,researchactivitieson5Gcommunicationtechnologieshaveemergedinboththeacademicandindustri-alcommunities.Variousorganizationsfromdif-ferentcountriesandregionshavetakeninitiativesandlaunchedprogramsaimedatpotentialkeytechnologiesof5G:5GNOWandMETISlaunchedundertheEuropeanTelecommunica-tionsStandardsInstitute’s(ETSI’s)Framework7studynewwaveformsandthefundamentalsof5Gtomeettherequirementsin2020;the5GResearchCenterwasestablishedintheUnitedKingdomtodevelopaworld-classtestbedof5Gtechnologies;theThirdGenerationPartnershipProject(3GPP)hasdrawnupitsdraftevolutionroadmapto2020;andChinahaskickedoffitsIMT-2020Forumtostartthestudyofuserdemands,spectrumcharacteristics,andtechnolo-gytrends[1].Thereisabroadconsensusthat5Grequirementsincludehigherspectralefficiency(SE)andenergyefficiency(EE),lowerend-to-endlatency,andmoreconnectionnodes.FromtheperspectiveofChinaMobile,5Gshouldreflecttwomajorthemes:greenandsoft.Asglobalcarbonemissionsincreaseandsealevelsrise,globalweatherandairpollutioninmanylargecitiesacrosstheworldisbecomingmoresevere[2].Consequently,energysavinghasbeenrecognizedasanurgentissueworldwide.Informationandcommunicationstechnologies(ICT)takeupaconsiderableproportionoftotalenergyconsumption.In2012,theannualaveragepowerconsumptionbyICTindustrieswasover200GW,ofwhichtelecomsinfrastructureanddevicesaccountedfor25percent[3].Inthe5Gera,itisexpectedthatmillionsmorebasesta-tions(BSs)withhigherfunctionalityandbillionsmoresmartphonesanddeviceswithmuchhigh-erdatarateswillbeconnected.Thelargestmobilenetworkintheworldconsumedover14billionkWhofenergyin2012initsnetworkof1.1millionBSs.Ifgreencommunicationstech-nologiesareuniversallydeployedacrossthisnet-work,significantenergysavingscanberealized,enablinglargerinfrastructuredeploymentsfor4Gand5Gcapacityupgradeswithoutrequiringsignificantincreaseinaveragerevenueperuser(ARPU).DramaticimprovementsinEEwillbeneeded;consequently,newtoolsforjointlyopti-mizingnetworkSEandEEwillbeessential.SeveralresearchgroupsandconsortiahavebeeninvestigatingEEofcellularnetworks,includingMobileVCE,EARTH,andGreen-Touch.MobileVCEhasfocusedontheBShard-ware,architecture,andoperation,realizingenergysavinggainsof75–92percentinsimula-tions[4].EARTHhasdevisedanarrayofnewtechnologiesincludinglow-lossantennas,microdirecttransmission(DTX),antennamuting,andadaptivesectorizationaccordingtotrafficfluctu-ations,resultinginenergysavingsof60–70per-centwithlessthan5percentthroughputdegradation[5].GreenTouchhassetupamuchmoreambitiousgoalofimprovingEE1000timesby2020[6].Severaloperatorshavebeenactivelydevelopinganddeployinggreentechnologies,includinggreenBSspoweredsolelybyrenew-ableenergies,andgreenaccessinfrastructuresuchascloud/collaborative/cleanradioaccessnetwork(C-RAN)[7].Carriergradenetworksarecomplexandcom-posedofspecial-purposenodesandhardware.Newstandardsandfeaturesoftenrequireavari-etyofequipmenttobedevelopedandintegrat-ed,thusleadingtoverylonglaunchcycles.InordertoaccommodatetheexplosivemobileABSTRACTAsthedeploymentandcommercialoperationof4Gsystemsarespeedingup,technologistsworldwidehavebegunsearchingfornextgenera-tionwirelesssolutionstomeettheanticipateddemandsinthe2020eragiventheexplosivegrowthofmobileInternet.Thisarticlepresentsourperspectiveofthe5Gtechnologieswithtwomajorthemes:greenandsoft.ByrethinkingtheShannontheoremandtraditionalcell-centricdesign,networkcapacitycanbesignificantlyincreasedwhilenetworkpowerconsumptionisdecreased.Thefeasibilityofthecombinationofgreenandsoftisinvestigatedthroughfiveinter-connectedareasofresearch:energyefficiencyandspectralefficiencyco-design,nomorecells,rethinkingsignaling/control,invisiblebasesta-tions,andfullduplexradio.5GWIRELESSCOMMUNICATIONSYSTEMS:PROSPECTSANDCHALLENGESChih-LinI,CorbettRowell,ShuangfengHan,ZhikunXu,GangLi,andZhengangPan,ChinaMobileResearchInstituteTowardGreenandSoft:A5GPerspectiveROWELL_LAYOUT.qxp_Layout1/30/141:23PMPage66IEEECommunicationsMagazine�February201467Internettrafficgrowthandalargenumberofnewapplications/servicesdemandingmuchshort-ertimestomarket,muchfasterturnaroundofnewnetworkcapabilitiesisrequired.DynamicRANreconfigurationcanhandlebothtemporalandspatialdomainvariationofmobiletrafficwithoutoverprovisioninghomogeneously.Softtechnologiesarethekeytoresolvetheseissues.Byseparatingsoftwareandhardware,controlplaneanddataplane,buildingsoftwareovergeneral-purposeprocessors(GPPs)viaprogram-minginterfacesandvirtualizationtechnology,itispossibletoachievelowercostandhighereffi-ciencyusingsoftwaredefinednetworks(SDNs)andnetworkfunctionsvirtualization(NFV)[8].TheOpenRoadprojectatStanfordUniversityintroducedOpen-flow,FlowVisor,andSNMPVi-sortowirelessnetworkstoenhancethecontrolplane.BasestationvirtualizationfromNECcon-centratedonslicingradioresourcesatthemedi-umaccesscontrol(MAC)layer.CloudEPCfromEricssonmodifiedLongTermEvolution(LTE)controlplanetocontrolopen-flowswitches.CellSDN