Upload
others
View
3
Download
0
Embed Size (px)
Citation preview
DOI: 10.4018/IJWNBT.2017010104
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
Copyright©2017,IGIGlobal.CopyingordistributinginprintorelectronicformswithoutwrittenpermissionofIGIGlobalisprohibited.
Analyzing Small-Cells and Distributed Antenna Systems from Techno-Economic PerspectiveChristos Bouras, Computer Technology Institute and Press “Diophantus”, Patras, Greece & Computer Engineering and Informatics Dept., University of Patras, Patras, Greece
Vasileios Kokkinos, University of Patras, Patras, Greece
Anastasia Kollia, University of Patras, Patras, Greece
Andreas Papazois, University of Patras, Patras, Greece
ABSTRACT
Thenewgenerationsofmobilenetworkswillrequireeconomicalandviablesolutionsinordertomeetthepromisesraisedbyscientists.Inthisarticle,theauthorsoverviewtheavailableresearchactivitiesandpresentanarchitectureforDASandfemtocellsandamathematicalmodelanalyzingtheircosts,astheyareconsideredtechnologies,thatoffergreatadvantagesformobilenetworks.Theauthorspresentawideresearchinthesolutions’parametersandprices.Therearethoroughexperimentsincludingseveraldifferenttypesofcosts.Inparticular,Capital(CAPEX),Operational(OPEX)expendituresandTotalCostofOwnership(TCO)areexaminedforbothtechnologiesintermsofthebackhaulingtechnologies,ofthesizeofbuildingsthattheyareimplementedinandtheyearsofinvestmentfromatelecommunicationcompany.Themainresultsarethatfemtocellsareamoreappealingsolutionwhenitcomestosmallplaces,whilethealternativeismorefavorableforbiginfrastructures.
KEyWoRDS5G, DAS, Femtocells, Small-Cells, Techno-Economic Analysis, Ultra-Dense
1. INTRoDUCTIoN
Next-generationofmobiletechnologiesisexpectedtolargelyaugmentthesystem’speakdataratesandcutdownontheround-tripdelays.Themainideaofusingultra-densityorDAS(DistributedAntennaSystems)basedontheirproperties,isthattheyareabletoincreaseefficiencyandexpandnetworkcapacitywithouttheneedformorespectrumresourcesbyredistributingtheexistingones,depictthemasthekeysolutionsforthefuturemobilenetworks.SmallcellsandDASwerelaunchedmainlyforaddressingtheissueoflimitedconnectivityindoors.
Thereareseveralotherimportantbenefitsofthesetechnologies,whichconstitutethemasbasesforfuturegenerationsofmobilenetworks,suchas5G(5G-PPP,2014).Femtocells’benefitisthattheyprovideultra-density,whichisexpectedtobeoneoftheessentialfeaturesof5G.Ultra-densenetworkscoexistwiththeexistingmacrocellularonesformingaltogetherheterogeneousnetworksandfulfilltherequirementsandthenetwork’sfuturedemands.Scientistsandresearchershavedecidedtomovetowardsthisdirectionbyconductingresearchactivityinthearea(Networld2020ETP,2014;IWPC,2014).
45
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
46
Thefuturemobilenetworksaregoingtodemandalargenetworkcoverage.DASwouldbeanidealsolutiontodealwiththelimitedspectrum,becauseitprovidesrepeaters,thatareconnectedtotheantennasystem.Italsoservestheaugmentingnumbersofthesmartdevices,thatinthefuturewillbeconnectedtotheInternetorthesmarthomedevicesoftheowner’shomenetworkaswemovedynamicallytotheInternetofThings.
Thispaperstudiesthetechno-economicaspectsofultra-denseandDASdeployments.Itpresentsthecharacteristicsandadvantagesforalltheirparts,aswellasatechno-economicmodelingofthesedeploymenttypes.Thedefinedmodelsareusedfortheinvestigationoftheuppertechnologiesfromaneconomicpointofview.Theyprovideaninsightinthefuturefinancialandpricingaspectsofthesesolutionsandconsistausefultoolforthedefinitionoffinancingandpricingpoliciestowardseconomicallyviabledeployments.The authors definemodels for selecting themost appropriatenetworkarchitecturalsolutionforpublicbuildings’ indoorcoverage.Cost, investment,materials,coverageandcapacityaretheparametersthataretakenintoaccountforthedefinitionoftheirmodels.Themainscientificcontributionofthispaperisthatitincludesmultiplecase-studyexamplesofthetechno-economicmodelsaswellasresultsofconductedexperiments.Italsoanalyzesandpresentsatechno-economicmodelandsummarizesthemainresearchactivityintheparticularfield.
Theremainingpartofthispaperisstructuredasfollows:thesecondsectionreferstotherelatedresearchthathasbeenconductedsofar.Thethirdsectionpresentsthearchitecturesofultra-denseandDASdeploymentsusedinthemodels.Inthefollowingsectionwedescribecostmodelsforultra-denseandDASdeployments.Inthenextsectionwedefinetheparameterizationofthecostmodels.Inthesixthsectionweconducesomeexperimentalscenariosandanalyzethecorrespondingresults.Finally,intheseventhsectionweconcludeourpaperwiththemostfundamentalconclusionsrealizedintheexperimentalprocedureandinthefinalsectionwelistsomeideasforfutureresearchworkinthefieldofmobilenetworktechnologies.
2. RELATED WoRK
Inthissection,itisofmajorimportancetopresentthemostvaluablestudiesthathavebeenconductedinthefield.Therecordofthemostvaluablepastresearchactivityisgoingtoindicatethepathsthatfuturescientificresearchshouldfollowdescribingmobilenetworkdeployments.
Inliterature,theDASsystem’smostvaluablestudiesare(Liu,2013;Liuetal.,2012),thatexaminetechnologicalandeconomicaspectsofthetechnologyandcomparetheTotalCostofOwnership(TCO)betweenDASandfemtocells,leadingtothefactthatfemtocelldeploymentsarecheaperthantheDASones.TherearenotanyothervitalstudiesinthefieldofDASdeployments,soitisimportanttopointouttheneedofinvestigatingit.
Thereexistssubstantialactivityinthefieldofsmallcells.Scientistshavealreadystudiedthetechnologicalaspects,suchascognitiveradio,self-organizednetworks,andradioresourcemanagementleadingtoasignificanttechnologicalbackground.Literaturereviewisindicatingthattechno-economicaspectsofsmallcellshavenotbeenfullyresearched,althoughtherearefundamentalworksthathavebeenpublishedsofar,like(Shettyetal.,2009)thatreferstotheeconomicadvantagesthatstemfromthecombinationofthemacrocellsandthefemtocellsfortheoperatorand(Claussenetal.,2007)thatadequatelyinvestigatesthecostofthenetworkforthepredecessoroffemtocell,thepicocell.Scientists,butmostly the telecommunicationandnetworkoperatorsare interested in the techno-economicaspects.Similarworksliketheonedescribedin(Nikolikjetal.,2014)examineseveraldeploymentstrategiesfromacostperspective.
Theauthorsofthispaperhavealsopresentedanintroductiontothepresentworkin(Bourasetal.,2014),wheretheyanalyzemodelsforfinancingandpricingsmallcellandmacrocellserviceandcomparewhichcaseisthemostfavorablefromtheperspectivesofusersandoperators.(Markendahletal.,2010)comparesthetwomaintechnologiesmacrocellsandfemtocellsconductingimportantconclusionsforthecostswhetherornotanewbasestationisformed.Accordingtothisresearch,if
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
47
abasestationisneeded,thenthemacrocellsremainaneffectivealternative.The(Fratuetal.,2014)referstoapurelytechnologicalanalysisofthefemtocelltechnology,analyzingtheinterference,energyefficiencyandspectrumefficiencyinheterogeneousnetworks.Thetechno-economicanalysis(Yunasetal.,2014)presentsathoroughinvestigationofsmallcells,microcellsandmacrocellsbytakingintoaccountfactors,suchasthecoverage,thecapacity,theenergyandthecostefficiency.Theresearchendsupconcludingthatultra-densityisthemainkeyto5G.In(5G-PPP,2014;Networld2020ETP,2014)arediscussedtheunderlyingdemandsoftheadventof5G.Themostimportantdemandsof5Gareaugmentednetworkcapacity,morecoverage,betterredistributionoftheavailableresources,safernetworkconnectionetc.
3. ALTERNATIVE DEPLoyMENTS
Inthissection,weanalyzethemostvaluablecharacteristics,thatsmallcellsandDASdeploymentspresentanddepicttheirbasicstructures:
3.1. Small CellsAccordingtoNetWorld2020in(Networld2020ETP,2014),5Gmobilenetworksshouldalsoprioritizetheprovisionofmethodsforflexiblepricingmechanismsandsmallcellsconstituteasuggestionthatoffersmanypossibilities.Inparallel,theInternationalWirelessIndustryConsortium(IWPC)stressesthevitalityofultra-densificationinnextgenerationofcellularsystems,i.e.,the5Gsystems(IWPC,2014).Itisconsideredthatultra-densificationFigure2isthefundamentalrequirementthat5Gsystemsshouldmeetinordertoachievefundamentalrequirements,suchas:
• 50xtimesmorecapacity(competentspectralefficiency,wideravailablespectrum)(IWPC,2014).• Peakdataratesexceeding10Gbit/s.• Ultra-lowlatencybelow1msec.
Thesetypesofdeploymentareexpectedtobecomeextremelyefficient,whentheyareaddressedinplaceswheretrafficpatternsarehighasdescribedinFigure1.
Ultra-densityoffersmanysignificantbenefits forsubscribersandmobilenetworkoperators.Onekeyevolutioninmobilenetworksistheshiftfromcellsofferinglargecoveragetoprogressively
Figure 1. The proximity of the cells in Ultra-dense deployments
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
48
smallercells,andultimatelyleadingtosuper-densedeployments.Ultra-densitybringsbasestationnexttothemobiledevice.Subsequently,itoffersthefollowingbenefitstoend-users:
• Higherthroughputaswellaslowerround-tripdelays.• Improvementinindoorcoverageduetointernalbasestationdeployment.• Seamlesshand-offs fromoutdoors (macrocellular access) to indoors (small cell access) and
viceversa.• Closedusergroupaccessibility.Onthecontrary,totheopenusergroupaccess,enablesthechoice
ofpre-decisedgroupofusersordevicesthatwillaccessaparticularcell.• Strictersecurityprotocolsandalgorithms.
Additionally, apart fromcustomers’ satisfaction, thereare several importantbenefits for themobiletelecommunicationoperators.Themostfundamentalonesarethefollowing:
• Lowerexpendituresforobtainingthebasicassetsandfortheoperationofthesystem.• De-congestionofthemacrocellnetworkbyreusingspectrumfromthesmallcellsperspective.• Thespectrumredistributionaugmentsthenetwork’scapacity.• Powerconsumptionandenergycostsdiminish,becausesmallcellsarewell-knownforbeinga
greentechnologicalsolution.• Degradeproblemsandissuesoflawandadministrationthatarisefromthemacrocells’use.
Ultra-densityhasseveralsignificantbenefitsforbothsubscribersandmobilenetworkoperatorsthatmakeitanappealingserviceandasolutionthatcompetesuccessfullyagainsttheconventionalsolutions.Subscribersinterferewithoutspecialknowledgeintheterminalofsmallcells.Anotherimportantproblemsolvedbytheadoptionofthemicrocellulartechnologyistheoneofthehandovers.Smallcellsaremoresecurecomparedtoothersolutions,becausetheyofferthepossibilitytolimittheaccesspermissionswithinapreselectedgroup.
Ontheotherhand,thereareseveralchallengesthatultra-densedeploymentsface.Basedontheanalysispresentedin(Fratuetal.,2014),theyaresummarizedasfollows:
• Self-organizingnetworkfeatures,sinceoperatorswillnotbeabletoperformconventionalnetworkplanningoverultra-densedeployments.
Figure 2. There are many antennas and cells inside the coverage area of a bigger cell in Ultra-dense deployments
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
49
• Inter-cellinterference,becauseoftheexistenceofthefemtocelltierovertheexistingmacrocellularinfrastructure.
• Energyefficiencyfeatures,sincethetotalenergyconsumptionwillbelikelytoincrease.• Spectral efficiency features, which will enable the high re-usage of the available spectrum
resources.• Costefficiency,whichisnotonlyatechnicalchallengebutalso,isthemaintopicofthispaper.
3.2. DASAnotherpossiblesolutioninordertoaugmentthenumberofusersconnectedtothenetworkistheuseofaDASdeployment.DASFigure3isanetworkofspatiallyseparatedantennanodesconnectedviaacommonsourceviaatransportmediumthatprovideswirelessservicewithinastructure.ThereareseveralassetsintheusageofDASrelatedtomoreefficientcoverage,lowerpowerconsumptionetc.AtypicalDASconsistsofthefollowingcomponents:
• AnumberofremoteDASnodes,eachoneincludesatleastoneantennaforthetransmissionandoneforthereceptionofwirelessprovider’sRadioFrequency(RF)signals(2antennas).Thisstructureisequivalenttotheexistingconventionalantenna,butinthiscase,itsfunctionalityispartedinsmallerantennastructures.Thereisalsoagreatneedinsupportingassetsandequipment,suchasamplifiers,remoteradioheads,signalconvertersandpowersupplies.
• Ahighcapacitysignaltransportmedium.Thedesiredmediumisfiberopticcable,becausedoesnotincursignallossunlikeothercheapermeansoftransmission.
• Agreatvarietyofradiotransceivers,thatprocessandcontrolthetransmittedsignal.
Abasicstructureincludestwoantennasandtwofeedersperfloor.ThecaseofindoorDASisimplementedinsidebuildingsandincludesallthecomponentsmentioned.Ineachdown-linkexistsapassivefeeder.Ifthenumberofdevicesservedaugments,morethanonestructuresineveryfloorareintroduced.DAStechnologyalsohasseveralsignificantbenefitsforbothsubscribersandmobilenetworkoperatorsthatmakeitanappealingsolutionsuchas:
• Betterdefinednetworkcoverageandredistributedcapacity.• Manycoverageholesthatenablenetworkstoovercomethecapacityproblems.• Offeringofthesamecoverage,butlesspowerconsumptioncomparedtoothersolutions.• Thedistributedantennasarenotplacedinsuchhighaltitudesastheequivalentsingleones.
Ontheotherhand,someoftheissuesraisedbyDASopponentsarethefollowing:
• Highcosts,duetotheadditionalinfrastructures,thathavealreadybeenreferred.• Possiblehealthconcerns,duetogreatervisualimpactonusers.• Differentnetworkdesignthanthemicrocellularsolutions.• Expertiseforengineersfordesigningandmaintainingthenetwork.
4. CoST ANALySIS
Inthissection,itisofvitalimportancetomathematicallyassessthecostsoftheprevioustechnologies.Weproposethreefinancialmodelsthatareusedforthecostestimationofthetechnologicalcasespresentedbelow:smallcells,macrocellsandDAS.
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
50
4.1. MethodologyForthetwobasictypesofdeploymentformacrocellsandsmallcells,weassumetwotypesofcoststhecapital(CAPEX)andtheoperationalexpenditure(OPEX).TheCAPEXistheamountofmoneyanetworkoperatorspendsinordertoobtainnewequipment,sites,etc.Ontheotherhand,theOPEXsumstheexpendituresthatarerelatedwiththecosts thatoccurduringthewholeyearandcoverthebudgetneededformaintenanceandoperation.Previousstudies,haveadoptedaunitedpatternofcomputingthesecostsandhavefollowedthesamereasoning.Themethodologyispresentedin(Claussenetal.,2007),thatpointsouthowimportantistoestimatetheCAPEXandOPEXannually.CAPEXisforeseenforthenewequipmentbyusinganimportantassumption.CAPEXisconsideredtobealoan,soCAPEXisvaluedasthecapitalthatisacquiredthroughtheloan.Finally,theannualpaymentsfortheinstallationanddeploymentofthenewequipmentarethebudgetneededtorepaytheloan.
Figure 3. Description of the DAS system architecture of a building
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
51
Generally,itispossibletomakeanassumptionovertheloanofaprincipalamountP,whichshouldberepaidannually.Themoneyneededtoberepaidispresentedbytheannualinstallmentpayment,representedbyAandisexpressedbytherepeatingpaymenttype:
A Pr r
r
n
n=
+( )+( ) −1
11
(1)
whererrepresentstheperiodicinterestrateandnrepresentsthenumberofpayments,i.e.,thelengthoftheinstallmentplaninyears.
4.2. Ultra-Dense DeploymentInthissection,weanalyticallypresentthecoststhatbearasubscriberoranoperatorthatchoosestoimplementtheultra-densityinanetworkanditisimportanttopresentthetwocasesofexpendituresofultra-densedeployments.
4.2.1. Capital ExpenditureTheCAPEX isdescribedasexpenses that stemfrom thebase stationand the routersneeded tocontrolthenetwork’straffic.Thereisalsoatypeofcostthatisrelatedwiththecorenetworkofthemobileoperator.Thesecostsarethemostexpensiveones,thisiswhywedonotconsiderothercheaperexpenses,suchas thecost for theEvolvedPacketCore(EPC).Furthermore,weassumethattherealreadyexistsamobilenetworkoperatorthatprovidesabroadbandconnection.Thus,wedonotincludeinouranalysisthecostsforthebroadbandequipmentandthebackhaulequipment.TheCAPEX,basedonthehypothesisin(1)andassoonas,thebasestationcostisrepresentedbyCHeNBandthecostoftheinterfaceneededforthemanagementofthenetworkisrepresentedbyCi/f,thentheannualcostfortheinstallmentofanultradensedeployment,whichconsistsofNHeNBsisdescribedbythefollowingequation:
CNC
id nsCX i f
ne e
i=− +( )
/
1 1 (2)
CcxdensedenotestheannualtotalcostofCAPEXandNisthenumberofHeNBs.
C N C Cr r
rd nsCX
HeNB i f
n
ne e= +( )
+( )+( ) −
/
1
11
(3)
CcxdensedenotestheannualtotalCAPEXandNisthenumberofeNBsconsistingtheultra-dense
deployment.
4.2.2. Operational ExpenditureOPEXdoesnotincludetheexpensespresentedbelow:
• Siteleasingcostisignoredgiventhatthebasestationsareinstalledinthesubscriber’sproperty,soitisoftheuser’spointtopaythecosts.
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
52
• Powerconsumptionisnegligible,duetosmallcellsizeandenvironmentally-friendlyfeaturesandispaidbythesubscriber.
• Support and maintenance costs bare mainly the broadband service provider as well as thesubscriber.Thesmallcellisacquiredbythesubscriber,soifdamaged,heisobligedtoreplaceit.
Consequently,onlyonecostcategoryisconsideredintheOPEXfortheultra-densedeploymentand is thecost for theequipmentof routingmanagementof thenetwork.MaintenancecostsareconsideredlinearlyproportionaltoCAPEXandarecalculatedasCAPEXmultipliedwithacoefficientfst, that denotes bandwidth and site costs due to maintenance activities. Subsequently, OPEX isrepresentedbythefollowingequation:
C f NCr r
rd ns st i f
n
n
OXe e=
+( )+( ) −
/
1
11
(4)
Consequently,thefollowingequation:
C fNC
id nsTCO
m
i f
ne e
i= +( )
−( )1
1
/ (5)
whereCTCOdenseexpressestheTCOforsmallcelldeploymentthatbearsthemobilenetworkoperator’s
sideonanannualbasis.Thisexpressionisbasedon(2)and(3)anditshouldberemindedthatiistheinterestrateandnisthedurationoftheinstallmentplaninyears.
4.3. Macrocellular DeploymentInthissubsection,wepresentthebasiccoststhatareincludedinamacrocellulardeployment.Inthiscasealso,themacrocellularcostsaresplitinthetwosamesidesaspreviously.
4.3.1. Capital ExpenditureItrepresentsthecoststhataremadeinordertoexpandthecoreEPCnetwork.AssumingthatthesecostsareexpressedbyCeNBandCEPCrespectively,theamountofmoneyneededforonebasestationisgivenbytheexpression:CeNB+CEPC.ItissignificanttoestimatethecostofasingleevolvedNode-B(eNB),namelythemacrocellularbasestation.Itconsistsofthenetworkequipment,soweassumeCAPEXisrepresentedbythenetworkbasestationcosts,becauseitfullycoverstheeNBandtheEvolvedPacketCore(EPC).Forthatreason,thecostisdescribedbythefollowingexpression:CeNB+CEPC.TheamountsCeNBandCEPCarethecostsforeNBandEPC,whichisthetermusedforLongTermEvolution(LTE-A)’scorenetwork,respectively.ItisimportantthattheCeNBapartfromthecostsrelatedtotheeNBequipmentandimplementation,alsoincludesanyadditionalcostsforthesiteacquisition,constructionandeNB’sbackhaul.TheamountCEPCincludesallthecostsrelatedtothecorenetwork,suchascostsoccurforroutingthenetwork’straffic.
Usually, the macrocellular deployment consists of several base stations, the number ofmacrocellularbasestationsexistingisrepresentedbythecoefficientN,thatiscomputedinnumbersofbasestations,thenthetotalcostforallthebasestationsisgivenby:N(CeNB+CEPC).
IfwepresumethattheCAPEXforthemacrocellulardeploymentisaninvestmentamountN(CeNB+CEPC)thathastobemadeinadvance,thenbasedonthebasicassumption(1)wecanformthefollowingequationforthemacrocellularCAPEX:
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
53
C N C Cr r
rmaCX
eNB
n
nEPCcro= +( )
+( )+( ) −1
11
(6)
whereCcxmacrodenotestheannualtotalcostofCAPEX.
4.3.2. Operational Expenditurecrunisacoefficient,thatrepresentsthetotalannualcostsforrunningauniquesiteprovidingthecostsforpower,in-siteandoff-sitesupport,in-siteandoff-sitemaintenanceandalsointroducesacoefficientcbh,thatexpressesthebackhaulcosts,whateverthematerialofthebackhaulingis.WedescribetheannualOPEXCox
macrobythefollowingequation:C N C CmacroOX
run bh= +( ) (7)
Thecosts formaintaining thesiteare linearlyproportional to theCAPEXmultipliedwithacoefficientfmthatdenotescostsrelatedtotheoperationandalltherestsitecosts,forexampletheoperation,thesupportetc.aresummedbytheamountcst.Therefore,theamountNcrunisexpressedas:fmCCX
macro+Ncst.Whereas,thecoefficientcbhisnotonlyconsideredasthebackhaulcosts,butislinearlyproportionaltotheusedbandwidthBWmultipliedwithacoefficientfBW.Concluding,basedonalltheassumptionsabove,theannualOPEXasdescribedin(Liuetal.,2012)isexpressedas:
C f C Nc f BWmacroOX
m macroCX
st BW= + + (8)
or,bysubstitutingtheCAPEXprovidedby(6),theOPEXisrepresentedbytheequation:
f N C Cr r
rNc f BW
m eNB EPC
n
n st BW( )
( )+
+
+( )+ +
−
1
11
(9)
Reclaimingthe(6)and(11)theTCOformacrocellularforthetelecommunicationoperatorisrepresentedbythefollowingequation:
C f N C Cr r
rNc f BW
macroTCO
m eNB EPC
n
n st BW= + +
+
+( )+ +
−( ) ( )
( )1
1
11
(10)
CTCOmacrorepresentstheTCOforamacrocellularbasestation,iistheinterestrateandnisthe
durationoftheinstallmentplanexpressedinyears.crunrepresentsthemaincostpaidannually,duetorunningasinglesite,includingthecostsfor
energyconsumption,in-siteandoff-sitesupportandmaintenanceandcbhdenotestheexpendituresfortheintroductionofthebackhaulingtechnology.Thus,theannualOPEXCOX
macroisexpressedbythefollowingequation:C N C Cmacro
OXrun bh
= +( )
Wehavealreadyshownthatalltherestsitecosts(operation,support,etc.)areexpressedbytheamountcstandarelinearlyproportionaltotheCAPEX,whichismultipliedwithacoefficientfm.Therefore,theamountNcrunisfurtherexpressedas:fmCCX
macro+Ncst.Moreover,weindicatedthattheamountcbhrepresentsthebackhaulcostsandisconsideredtobelinearlyproportionaltotheusedbandwidthBWmultipliedwithacoefficientfBW.So,theannualOPEXissuedin(6),(10)isexpressedbythefollowingequation:
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
54
C f N C Cr r
rNc f BW
macroOX
m eNB EPC
n
n st BW= +
+
+( )+ +
−( )
( )1
11
(11)
Basedon(6)and(11)theTCOforthemobilenetworkoperatoronanannualbasisisexpressedbythefollowingequation:
C f N C Cr r
rNc f BW
macroTCO
m eNB EPC
n
n st BW= + +
+
+( )+ +
−1
1
11
( )( ) (12)
whereCTCOmacroistheTCOforamacrocellularbasestation,iistheinterestrateandnistheduration
oftheinstallmentplanexpressedinyears.
4.4. DAS DeploymentInthissubsection,thecostsfortheDASdeploymentisslightlydifferentfromthetwopreviouscases.TheTCOconsistsofthreemainparts:CAPEX,OPEXandIMPEX(ImplementationExpenditure).
4.4.1. Capital ExpenditureCAPEXhasalreadybeenconsideredandresearchedinthepastandincludesthecostsforthefollowingassets(Liuetal.,2012):
• TheDASbasestation,• Thedistributedsystem,suchastheremoteantennas,thepowersplitters,thewide-bandcombiners,
coaxialcableoropticfibercable,cableconnector,etc.• Thebackhaulequipmentwhetherisopticfiberorcoaxialcableandthesoftwarecost• Thesupportingequipment, suchasWallmountingkit, thepowercable, thebatterybackup,
possiblyexistingalarmsystem,etc.
TheDAS includes abase station that is similar to themacrocellularone, this iswhy,DASandmacrocellularbasestationsincludethesametypesofcosts.TheestimationofthecostsisthatCeNBrepresentsthecostforoneDASbasestation,aswellasanyothercoststhatstemfromthesiteacquisitionortheconstructionoranybackhaulcostsfortheeNBnodes.CEPCrepresentstheEPCcostsandaremadeforthenetwork’srouting.TheTCOforthenetworkequipmentisexpressedbythefollowingequation:CeNB+CEPC.
TheestimationoftheCAPEXfortheDASdeploymentshouldbemadeannuallybytakingintoconsiderationtheannualinstallmentpaymentsoftheinvestment.WepayatotalinvestmentplanforCAPEX.IfthereareNbasestations,thenthetotalbasestation’scostisexpressedbythesubsequentequation:N(CeNB+CEPC).Generally,theannualinvestmentplanforthebasestationisbasedonthecoststhataredescribedinsimilarnetworks,suchasthemacrocellularbasestationpresentedbytheCEPC(Bourasetal.,2014).
WeconsiderthattheCAPEXfortheDASbasestationdeploymentaccruesthefollowingbudgetN(CeNB+CEPC)thatneedstobeoverpoweredfromthebeginning,andbyusingthehypothesis(1)wecouldcalculatetheDASbasestationcosts.TheCAPEXestimationonanannualbasisfortheDASbasestationisexpressedbythefollowingequation:
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
55
C N C Cr r
rBS EPCCX
eNB
n
n= +( )
+( )+( ) −1
11
(13)
whereiistheinterestrateandnisthedurationoftheinstallmentplanexpressedinyears.Itisvaluabletoanalyzethenecessaryexpenditures,becauseoftheadditionalequipmentneeded
inaDASsystemfortheDistributedSystem.ThecoefficientCeqrepresentstheequipmentneededfortheDASstructuresandislinearlyproportionaltoanotherfactord,thatdependsonthetotalnumberoftheDASstructuresthatexistsinthedistributedsystem.Therefore,wedescribetheCAPEXfortheantennasystemannuallybyintroducingthesubsequentequation:
C C dDASEQCX
eq=
r r
r
n
n
1
11
+( )+( ) −
(14)
whereCCXDASEQ,denotestheannualtotalCAPEXfortheDASequipment.
ThecompleteDASCAPEXisthesumofthecostsofalltheDASfeaturesandisdescribedbythefollowingequation:
C N C Cr r
rC d
DAS eq EPCCX
eNB
n
n= +( )
+( )+( )
+−
( )1
11
(15)
whereCCXDASdenotestheannualtotalCAPEXforthewholeDASsystem.
4.4.2. Operational ExpenditureDASOPEXwasdescribedasthesumoftheaboveexpenditures(Liuetal.,2012):
• Costsofbackhauloperationsandmaintenance.Itispossibleforsomepartsofthebackhaultoneedreplacementafteraperiodoftime.
• Thebackhaulrent,ifthesiteisrent,• Theconsiderationofthepowerconsumptioncosts,becauseoftheenergyconsumption.• Theoff-sitesupport,• Thesitevisitfortroubleshootingormaintenance,• Theleasingcosts,incasethesiteisleased.
TheDASbasestationdenotescosts,suchascrunthatrepresentstheannualtotalcostforrunningasinglesite,alsocomputingtheenergyconsumption,in-siteandoff-sitesupportandmaintenanceandcbhdenotesthebackhaulcost.So,theOPEXfortheDASbasestationisdescribedasfollows:C N C CDASOX
run bh= +( ) (16)
Whereas, thecoefficientcbhexpresses thebackhaulcosts,whichare linearlyproportional totheusedbandwidth,thatisdescribedbythecoefficientBWmultipliedwithacoefficientfBW,thatrepresents thebackhaulcosts inrelationwith theavailablebandwidth.Tosimplify theproducedequations,weconsiderthatthemaintenancecostsarelinearlyproportionaltotheCAPEXmultipliedwithacoefficientfst,thatdenotestheoperationalandthesitecostsandwerepresentalltheotherkindsofexpendituresbytheamountcrunthatrepresentsthecostsforrunningaDASsystem.Thus,theOPEXforrunningtheDASbasestationisfurtherexpressedas:
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
56
NC f Crun st DAS
CX= (17)
whereNisthenumberofDASnodes,andCCXDASistheCAPEXoftheDAS.
Wecomputethecostsforthemaintenanceandoperationofthedistributedsystem.Thisincludesthemaintenanceoftheantennastructures,becauseoftheantennasandfeedersateveryfloorofthebuilding,butalsoincludesanyextraoccurringactivities.ThecoefficientCeqdenotesthecoststhatareincludedfortheDASassets,forexampletheantennasandthefeeders,thataresituatedineveryfloorofthebuilding.Subsequently,theannualOPEXforthedistributedsystemisexpressedbythefollowingequation:
C C dr r
rDASEQOX
eq
n
n=
+( )+( ) −1
11
(18)
The DAS system, such as every other network structure needs to consume power, in ordertooperate.It is therefore,significant, tointroducetheenergyconsumptioncostdescribedbythecoefficientCpwTosummarize,thetotalOPEXperyearfortheDAScellsisexpressedasfollows:
C N C C Nc f BW f C C C dr r
DASOX
run bh st BW st DASCX
pw eq
n
= + + + + + + ++
( ) ( )( )1
111
+( ) −r n (19)
4.4.3. Implementation ExpenditureIMPEXisthebudgetthattheownerofthesystemshouldpayifthecellularsiteismoved.Consequently,itdescribestheamountofmoneythatisspentandisassociatedwithplanningandinstallingthenetworkasreferredinformerresearch.Accordingto(Liuetal.,2012)itissplitinthefollowingcosts:
• Thecostsoftheinstallationofbasestations,• Thecostoftheinstallationofdistributedsystem,• ThecoordinationcostduetodisruptiveDASconstructionwork,etc.
TheinstallationexpenditureshavealreadybeenconsideredaccordingtotheCCXDASanalysis,
becausethemainassumptionusedincludeseveryassetofthedistributedsystem.Ontheotherhand,thereemergecoordinationcosts,becausewheneverweinstallsomenewDASequipment,itispossibletomakeadjustmentstotheexistingnetworkinordertosucceedthebestoperationofthetotalsystem.ThecostofinstallationandcoordinationisdescribedbyacoefficientCinc.So,thetotalIMPEXfortheDASisexpressedbythefollowingequation:
C CDASIX
inc= (20)
Finally,theTCOperyearforDASisdescribedasthesumoftheCAPEX,OPEXandIMPEX,soitisrepresentedbythefollowingequation:
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
57
C N C C C d f C C C d
r r
r
DASTCO
eNB EPC eq st DASCX
pw eq
n
= + + + + + +( )⋅
+
+( )( )1
1 nnN C C f BW C
run bh BW inc−+ + +
1( )
(21)
5. PRICING MoDELS
In thissection, it iscrucial toanalyze thepricingmodels,with theparametersand thevariablesincludedintheequationsinordertocalculateallcostsandrunseveralexperimentsinordertodeducefundamentalconclusionsfortheadoptionofthemostfavorabletechnology.Beforeconducinganyexperiments,itisofgreatvaluetomakeathoroughpresentationoftheparametersofthemodel.Theselectionoftheparametrizationremainsacontroversialissue.Manyoftheparametersarenotonlytimedependent,(e.g.someexpendituresareaugmentingordiminishingwhentimeelapses),butalsomarketdependent,becauseofthedifferentcostssomeassetsandworksmaypresentinalternativeeconomies.Analytically,theinstallationcostinanAfricanoranAsianeconomyisdefinitelycheaperthantheonespresentedintheEuropeanorAmericanmarkets.
Byconductingadetailedresearchactivity,wewerefinallyleadtotheparameters’andcoefficients’costsinGreecefortheyear2016forthecaseofanultra-densedeploymentbasedonfemtocellsandacorrespondingDASdeployment,thatarepresentedinTables1and2respectively.Inthetwotables,notonlywepresentthevaluesfound,butalsothepapersthattheoccurringexpendituresareincluded.WeoptedforthefollowingparametersbasedontheassumptionsmadeforthenetworkmarketforthenextyearsinEuropeancountries.Inpapers(Bourasetal.,2014;Correiaetal.,2010;Markendahletal.,2010)therearemanypricingdatawhenitcomestofemtocellsandsmallcells.(Liu,2013;Liuetal.,2012)presentathoroughinvestigationonDAScostsandparameters.
6. EXPERIMENTAL RESULTS
Inthissection,weconductedexperimentsforthedeployments’costs.Weanalyzethemostfundamentalsuggestionsthatarecombinedwiththecorrespondingtechnologiesandweendupreachingseveralvitalresults.Weconsiderasafundamentalfacttoshowhowthecostsfluctuateifthereisaneedincreatinganewbasestationfromscratch.Weapplythepricesfoundfromthethoroughresearchconducted and we tested our mathematical models. We consider, that the most important casesaretheCAPEX,theOPEXandtheTCO.Inparticular,weanalyticallypresentthefollowingthreetechnologicalsuggestions:
• Femtocells(FEMTO).• DASincludingthedeploymentofabrandnewmacrocellbasestation(DASNB).• DASwithoutincludingthedeploymentofthemacrocellbasestation(DASW/ONB).
Figure 4 depicted the CAPEX of the upper simple case experiments. It presents the maincomparisonofthethreeuppercasesforCAPEX.Unlike,whatweexpectedtheCAPEXforbothDASdeploymentsaremuchlowerthantheonespresentedbyfemtocells.Moreover,thecostsoftheDASarestableandtheaugmentationoftheantennasdoesnotaffecttheinvestmentexpenditure.Themacrocellbasestationcontributesslightlyinthecosts,becauseDASwithdeployinganewmacrocellbasestationisnotmoreexpensivethantheonewithoutconsideringsuchadeployment.Ontheotherhand,femtocells’costsarelinearlyproportionaltothenumberoftheantennasaddedandwhenthenumberofantennasisincreasingtheexpendituresareaugmentingtoo.
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
58
TheoperationalexpendituresforpreviouscasesarepresentedinFigure5.TheexactoppositefactfromtheonepresentedinthecaseofCAPEXishappeningforthisanalysis.Alltheexpendituresarestable,whenthenumberofantennasaugments,butinthiscase,femtocellspresentlowercosts.Ontheotherhand,DAS’operationalexpendituresareveryhighandasamatteroffactcontributealottoitsTCO.Also,intheDAScasesthedeploymentofthemacrocellbasestationcontributestosomemoreexpensesandassiststothefactthatitisthehigherofallthepresentedcosts.DASTCO
Table 1. Cost Parameters and System Variables of DAS
Parameter Description Value
CeNB CapitalcostforEnb 1000€(Bourasetal.,2014)
CEPC Corenetwork’scapitalcostforthedeploymentofasingleeNB 110€(Markendahletal.,2010)
Ν ThetotalnumberofeNB’sandEPC’sneeded 1(Bourasetal.,2014)
i Annualinterestrate 6%(Bourasetal.,2014)
n Durationofinstallmentplanofasiteinyears 10yrs(Bourasetal.,2014)
r Periodicinterestrate 6%(Bourasetal.,2014)
Ceq CostofDASequipment 11900€(Liu,2013)
d FactorrelatedtothenumberofDASstructures 0.002
fst Linearcoefficientcorrelatingsitemaintenancecostswithcapitalexpenditure
0.8(Johanssonetal.,2005)
cst Sitecostsapartfrommaintenancecostswithcapitalexpenditure
3100€(Correiaetal.,2010)
Crun Runningcosts,suchassinglesite,in-site,off-site 892.5€(Liuetal.,2012)
Cbh Backhaulcostsformicrowave/opticfiber 3800€/4800€(Liu,2013)
BW Backhaulbandwidthforasite’sinterconnection 10Gbps(Bourasetal.,2014)
fBW Linearcoefficientcorrelatingsiteannualbackhaulcostswithprovidedbandwidthexpressedin€/Gbps
1170(Bourasetal.,2014)
Cpw OperationalcostsfortheenergyconsumptionoffemtocellOPEXcosts
157.68€(Liu,2013)
Cinc Implementationcostsfortheinstallationandthecoordinationofthesystem
2800€(Liu,2013)
Table 2. Cost Parameters and System Variables of femtocells
Parameter Description Value
CeNB CapitalcostforEnb 1000€(Bourasetal.,2014)
CEPC Corenetwork’scapitalcostforthedeploymentofasingleHeNB
110€(Markendahletal.,2010)
Ν ThetotalnumberofHeNB’sandEPC’sneeded 1(Bourasetal.,2014)
i Annualinterestrate 6%(Bourasetal.,2014)
n Durationofinstallmentplanofasiteinyears 10yrs(Bourasetal.,2014)
r Periodicinterestrate 6%(Bourasetal.,2014)
fm Linearcoefficientcorrelatingsitemaintenancecostswithcapitalexpenditure
0.8(Johanssonetal.,2005)
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
59
isveryexpensive,becauseofitshighOPEXanditisstable,whilefemtocells’TCOissmaller,butaugmentslinearlyproportionaltotheantennas’augmentation(Figure6).
Inaddition,examiningtheTCOFigure7fordifferentbackhaultechnologies,whenthenumberofantennasaugments,theTCOsofbothDASdeploymentsarehigher,butarefixedamounts.TheDASdeploymentswithamacrocellularbasestationarehigher,thantheotherswithoutimplementingthebasestation.Thebackhaultechnologydoesnotaffectmuchthecosts,althoughthehighercostisnotedfortheDAScasewithformingamacrobasestationandusingfiberasbackhaultechnology.So,itenablesnetworkoperatorstoaddopticfibers.Femtocells’expendituresaugmentlinearly,whilethenumberofantennasisincreasing.IntherespectivecaseofCAPEXpresentedinFigure8,theDASwithoutabasestationdeploymentformicrowaveorfiberislowertotheotherones.DASCAPEXislow,whilefemtocells’islinearlyaugmentingwhileaddingseveralantennas.
Figure 4. The comparison of the CAPEX for DAS and Femtocells
Figure 5. The comparison of the OPEX for DAS and Femtocells
Figure 6. The comparison of the TCO for DAS and femtocells
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
60
Itiscrucialtopointouttheneedofstudyingthecaseofaverylargeinfrastructure.Supposingseveral decades or a hundred of antennas needed Figure 9, we conclude that the DAS’ TCOexpendituresarestableandhigh.TheDASwithdeployingamacrocellularstationareonceagainhigherthantheotherswithoutthedeploymentofthemacrocellbasestation.Ontheotherhand,thefemtocells’costsarelinearlyproportionaltothenumberofantennasaddedinthesystem.Foronehundredantennas,thefemtocells’expendituresequaltheDAScosts.ThesameexperimentalprocedurefortheCAPEXisdepictedinFigure10,whileincreasingthenumberofantennasthefemtocells’CAPEXisthehighestoneasitislinearlyproportionaltothenumberofantennasadded.ForbothcasesofDAS,theCAPEXareextremelylowerandstablecomparedtothefemtocells’andtheonewiththedeploymentofabasestationremainshigherthantheonewithoutimplementingit.
Figure 7. The comparison of the TCO for DAS and femtocells for different backhaul solutions
Figure 8. The comparison of the CAPEX for DAS and femtocells for different backhaul solutions
Figure 9. The comparison of the DAS and femtocells for very large buildings
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
61
WedepicttheTCOinFigure11consideringtheinstallmentplanovertheyears.TheTCOisextremelyhigh,inbothDASdeploymentswhilethefemtocells’costsseemtodecrease,whileyearselapse.Forexample,fromtwotofouryearstheexpendituresarehigherthantheyareinthenextyears.Fromsixtotwentyyearstheexpensesstabilize.TheDAS’costsarehighercomparedtothefemtocells’.TheCAPEXforalldeploymentsfollowaparabolicorbit.Analytically,thetwocasesofDASandtheoneoffemtocellsdecreasewhiletimeelapses,butfemtocells’CAPEXishigherthanthoseoftheDAS’.TheCAPEXcostsaredepictedinFigure12.CAPEXisdecreasingwiththeelapsingofyearsforallcases.ThefluctuationislargerforthefemtocellcaseandsmallerfortheDAScases.
FromthepreviousexperimentsweconcludethatDASisslightlydifferentcomparedtofemtocells,afactalsodepictedintheircosts.DAScontributestoanoperatormuchOPEXandasaresult,itis
Figure 10. The comparison of the CAPEX for DAS and femtocells for very large buildings
Figure 11. The comparison of the TCO for the investment plan for DAS and femtocells over the years
Figure 12. The comparison of the CAPEX for the investment plan for DAS and Femtocell over the years
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
62
fundamentaltoreduceOPEXviadiminishingpowerconsumptionandintelligentnetworkmanagementpractices.Ontheotherhand,femtocell’sCAPEXislarger,butmostlyburdensasubscriberthatoptsforobtainingit.Accordingtotheapplication,onecouldoptforthemoreconvenientdeployment.DAScoversalargerarea,butcostsmoreandfemtocellscoveracoupleofusers.
Finally,wepointoutthattheexperimentalproceduresandtheresultsdescribethesituationoftheGreekmarketin2016andtherefore,Tables1and2presenttheparametersandcoefficients,thatappearintheGreekmarket.Itispossibletoparameterizetheproblemwithdifferentcostvaluesforothermarkets for futureexperimentalcases.Theparametersareobtainedvia thorough literatureactivityinthefieldoftelecommunications.Thisstudyisdifferentfromothersimilarones,becauseitgathersmanycasesoffemtocellsandDAS.Itcontributeselaboratingonthesubjectandconcludesaboutalltheimportantmattersraisedbefore.
7. CoNCLUSIoN
In this paper,wepresented several experiments for the cost calculationof femtocells andDAS.TCOforfemtocellsislowerthanthecostsofDASformostcases.WeexaminedTCO,CAPEXandOPEXforthetwosuggestions,experimentingwiththenumberofantennasinaccordancewiththebackhaulingtechnology,theyearsofinvestmentforthedeploymentoftechnologiesandtheverylargebuildingsthatincludemanyantennas.
Inmostcases,femtocellscostlessthanDAS.Forverylargeplaces,femtocellsarenotafavorablesolution,becausetheexponentiallyaugmenttheirTCOandfinally,costmorethanDAS.Ontheotherhand,DASiscosteffectivewhenitcoversalargeareawithoutahighaugmentationofcosts.Forlittleareas,thecoverageprovidedbyfemtocellsishelpfulandthecoststheyinducearelowandaffordablebyasinglesubscriber.DASimpartslargerOPEX,soitwouldbevitaltechniquestobedevelopedtodecreasethesetypesofcosts.FemtocellsinducelowOPEX,becauseevenanotexpertuserisabletofixsomeproblemsraisedandplacementandmaintenancecostsaretheminimumpossible.CAPEXislargerforfemtocells,butauserquicklydepreciateshisinvestmentwhenusesthem,especiallyreclaimingpossibilities,theyoffersuchasaccessibilitytootherusers.
8. FUTURE WoRK
Inthefuture,alargeamountofscientistswillbeinterestedinthemobilenetwork’scostcalculationandwilluseourstudy,inordertoconductseveralexperimentsandinduceawiderangeofimportantconclusionsintheexpenditurecases.Thisstudypresentsaflexibility,thatisrelatedtothefactthatitmathematicallydescribesthemodel,soitiseasyforascientisttoapplynewpricesinthefutureorpricesofadifferentmarket,notnecessarilyEuropeanorGreek.Inthenextyears,wesuggestthatscientistsshoulddealwithothersignificantissuesaswell,suchastheexpendituresrelatedtothebandwidth,thedepreciationforeachtechnology,thepowerconsumption,thetechnology’slife-cycle,theusage,thebasestationcostsoreventhedensityofthedeployments,improvingthesuggestedmodelanddiminishingtheOPEXcostsofDAS.
Scientistswoulddealwithahugevarietyofselectionsforfemtocells,suchasusergroupselection,femtocellsafety,reductionofpowerconsumption,reductionofbasestationcosts.Marketingandmanagementforwardingconvincingusersaboutthebenefitsoffemtocellsshouldalsobeconsidered.Thereisalsoaneedindelineatingthefutureoffemtocellscombinedwithotherdifferenttechnologicalsuggestions, such as Software Defined Networking in Wireless Networks and the way of theirmanagementbytheSDNsoftware.DASshouldbeinvestigatedinordertodiminishitsbasiccostsforboththeindoorandoutdoorcasesandalternativestoreducetheirhighOPEXshouldbeproposed.Thereshouldalsobeaninvestigationforhealthconcernsalongsidewithimposingexactlegislationconsideringthesetechnologies.
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
63
REFERENCES
Bouras, C., Kokkinos, V., & Papazois, A. (2014). Financing and Pricing Small Cells in Next-GenerationMobileNetworks.InWired/WirelessInternetCommunications(pp.41-54).SpringerInternationalPublishing.doi:10.1007/978-3-319-13174-0_4
Claussen,H.,Ho,L.T.,&Samuel,L.G. (2007,June).Financialanalysisofapico-cellularhomenetworkdeployment.InProceedings of the IEEE International Conference on Communications ICC’07(pp.5604-5609).doi:10.1109/ICC.2007.929
Correia,L.M.,Zeller,D.,Blume,O.,Ferling,D.,Jading,Y.,Gódor, I.,&VanDerPerre,L.et al. (2010).Challengesandenablingtechnologiesforenergyawaremobileradionetworks.IEEE Communications Magazine,48(11),66–72.doi:10.1109/MCOM.2010.5621969
ECH20205GInfrastructurePPP.(2014,June).Pre-structuringmodel:RTD&INNOstrands.Technicalreport,5thGenerationPublic-PrivatePartnership.
Fratu,O.,Vulpe,A.,Craciunescu,R.,&Halunga,S.(2014).SmallCellsinCellularNetworks:ChallengesofFutureHetNets.Wireless Personal Communications,78(3),1613–1627.doi:10.1007/s11277-014-1906-9
Johansson,K.,&Furuskär,A.(2005,May).Costefficientcapacityexpansionstrategiesusingmulti-accessnetworks.InProceedings of the 61st IEEE Conference on Vehicular Technology (VTC ’05)(Vol.5,pp.2989-2993).IEEE.doi:10.1109/VETECS.2005.1543895
Liu,Z.(2013,December).Techno-economicalAnalysisofIndoorEnterpriseSolutions[PhDthesis].AalborgUniversity.
Liu,Z.,Kolding,T.,Mogensen,P.,Vejgaard,B.,&Sørensen,T.(2012,September).Economicalcomparisonofenterprisein-buildingwirelesssolutionsusingDASandFemto.InProceedings of theIEEE Conference In Vehicular Technology (VTC Fall).IEEE.doi:10.1109/VTCFall.2012.6399316
Markendahl,J.,&Mäkitalo,Ö.(2010,September).Acomparativestudyofdeploymentoptions,capacityandcoststructureformacrocellularandfemtocellnetworks.InProceedings of the 2010 IEEE 21st International Symposium Personal, Indoor and Mobile Radio Communications Workshops (PIMRC Workshops)(pp.145-150).IEEE.doi:10.1109/PIMRCW.2010.5670351
NetWorld2020ETPExpertWorkingGroup.(2014).Nextgenerationofwirelessnetworks.Technicalreport.
NetWorld2020ETPExpertWorkingGroup.(2014).Whatis5G(really)about?Technicalreport.
Nikolikj,V.,&Janevski,T.(2014).Costmodelingofadvancedheterogeneouswirelessnetworksunderexcessiveuser demand. In Wired/Wireless Internet Communications (pp. 68-81). Springer International Publishing.doi:10.1007/978-3-319-13174-0_6
Shetty,N.,Parekh,S.,&Walrand,J.(2009,November).Economicsoffemtocells.InProceedings of theIEEE Global Telecommunications Conference, 2009 (GLOBECOM 2009).IEEE.
UltraHighCapacityNetworksWhitePaper. (2014,April).Evolutionary&disruptivevisions towardshighcapacitynetworks(Technicalreport).InProceedings of the International Wireless Industry Consortium (IWPC).Retrievedfromhttp://www.iwpc.org/WhitePaper.aspx?WhitePaperID=17
Yunas,S.F.,Niemela, J.,Valkama,M.,& Isotalo,T. (2014,September).Techno-economical analysis andcomparisonoflegacyandultra-densesmallcellnetworks.InProceedings of the IEEE 39th Conference Local Computer Networks Workshops (LCN Workshops)(pp.768-776).IEEE.doi:10.1109/LCNW.2014.6927733
International Journal of Wireless Networks and Broadband TechnologiesVolume 6 • Issue 1 • January-June 2017
64
Christos Bouras is Professor in the University of Patras, Department of Computer Engineering and Informatics. Also he is a scientific advisor of Research Unit 6 in Computer Technology Institute and Press - Diophantus, Patras, Greece. His research interests include Analysis of Performance of Networking and Computer Systems, Computer Networks and Protocols, Mobile and Wireless Communications, Telematics and New Services, QoS and Pricing for Networks and Services, e-learning, Networked Virtual Environments and WWW Issues. He has extended professional experience in Design and Analysis of Networks, Protocols, Telematics and New Services. He has published more than 400 papers in various well-known refereed books, conferences and journals. He is a co-author of 9 books in Greek and editor of 1 in English. He has been member of editorial board for international journals and PC member and referee in various international journals and conferences. He has participated in R&D projects.
Vasileios Kokkinos obtained his diploma from the Physics Department of the University of Patras on October 2003. Next, he was accepted in the postgraduate program “Electronics and Information Processing” in the same department and on March 2006 he obtained his Master Degree. In 2010 he received his PhD on Power Control in Mobile Telecommunication Networks from the Computer Engineering and Informatics Department. He works in the Research Unit 6 of Computer Technology Institute and Press “Diophantus” since September 2006. His research interests include data networks, third and fourth generation mobile telecommunications networks, multicast routing and group management and radio resource management. He has published several research papers in various well-known refereed conferences and articles in scientific journals.
Anastasia Kollia obtained the Proficiency in English of Michigan University in 2007. She obtained the “Diplome Approfondi de la langue francaise C2” de l’ “Institut francais” in 2007. She entered the Computer Engineering and Informatics Department in 2010 and obtained her diploma in 2015. She joined the ru6 of the Computer Engineering and Informatics Department at the University of Patras in 2014 and she has been a member ever since. She is currently a master student in the same department in the Computer Science and Technology. She is a member of the IEEE student branch at Patras since 2015. Her research interests include future mobile and wireless networks, Ultra-dense deployments and Software Defined Networking.
Andreas Papazois is a post-doctoral researcher at Computer Engineering and Informatics Department, University of Patras and an R&D engineer at GRNET S.A. In the past, he worked as telecommunications engineer in Intracom Telecom S.A. His research interests include future mobile networks, ultra-dense deployments and software defined networking. He has published several research papers in various well-known refereed conferences, books and journals. He has been technical committee member for several conferences and a reviewer for various scientific journals.