IEEEAcCeSSSPECIALSECTION ONRECENTADVANCESIN SOFTWAREDEFINEDNETWORKINGFOR5GNETWORKSReceived July 11, 2015, accepted July 22, 2015, date of publication July 28, 2015, date of current version August 7, 2015.Digital Object Idenrifier 10.1109/ACCESS.2015.2461602ASurveyof5GNetwork:ArchitectureandEmerging TechnologiesAKHILGUPTA,(StudentMember,IEEE),ANDRAKESHKUMARJHA,(SeniorMember,IEEE)School of Electronics and Communication Engineering. Shri Mata Vaishno Devi University, Katra 182320, IndisCorresponding author: A.Gupta (akhilguptal12001@gmail.com)ABSTRACT In the near future, i.e., beyond 4G, some of the prime objectives or demands that need tobe addressed are increased capacity,improved data rate, decreased latency, and better quality of service.To meet these demands, drastic improvements need to be made in cellular network architecture. This paperpresents theresults of adetailed survey on the fifthgeneration (5G)cellular network architecture and someof the key emerging technologies that are helpful in improving the architecture and meeting the demands ofusers.In this detailed survey,the prime focus is on the 5G cellular network architecture,massive multipleinput multiple output technology, and device-to-device communication (D2D). Along with this, some of theemerging technologies that are addressed in this paper include interferencemanagement, spectrum sharingwith cognitive radio, ultra-dense networks, multi-radio access technology association,full duplex radios,millimeter wave solutionsfor 5G cellular networks,and cloudtechnologiesfor 5Gradio access networksandsoftwaredefinednetworks.In thispaper,ageneral probable5Gcellular networkarchitecture isproposedwhich shows thatD2D,small cell access points,network cloud,and theInternet of Things can be a partof5G cellular network architecture.A detailed survey is included regarding current research projects beingconducted in different countries by research groups and institutions that are working on 5G technologies.:INDExTERMS5G,cloud,D2D,massiveMIMO,mm-wave,relay,small-cellLINTRODUCTIONeruption of new applications which will be used in casesforToday and in the recent future, to fulfill the presumptionsmobile connectivity and a resultant exponential growth inand challenges of the near future. thewirelessbased net-network traffic.This paper presents our view on the future ofworks of todaywill haveto advance in various ways.Recentwireless communication for 2020 and beyond. In this paper,technology constituent like high-speed packet access (HSPA)we describe the key challenges that will be encountered byand long-term evolution (LTE)wili be launched as afuture wireless communication whileenabling the networkedsegment of the advancement of current wireless basedsociety.Along with this,sometechnologyroutes thatmaybetechnologies.Nevertheless, auxiliary components may alsotaken to fulfill these challenges [1]constitute future new wireless based technologies,whichThe imagination of ourfuture is a networked society withmay adjunct the evolved technologies.Specimen of theseunbounded access to information and sharing ofdata whichnewtechnologycomponentsaredifferentways of accessingis accessible everywhere and every timefor everyone andspectrum and considerably higher frequency ranges, theeverything.To realize this imagination,newtechnology com-instigation of massive antenna configurations,direct device-ponents need to be examined for the evolution of existingwireless based technologies.Present wireless based techto-devicecommunication,andultra-densedeployments[1]Since its initiation in the late 1970s, mobile wirelessnologies,likethe3rdGenerationPartnershipProject(3GPP)LTE technology, HSPA and Wi-Fi, will be incorporating newcommunicationhascomeacrossfromanalogvoicecallstocurrent modern technologies adept of providing high qual-technology components that will be helping to meet the needsity mobile broadband serviceswith end-userdata rates ofofthefuture.Nevertheless,theremaybecertain scenariosthatseveral megabits per second over wide areas andtens, orcannot be adequately addressed along with the evolution ofeven hundreds,ofmegabits per second locally.Theextensiveongoing existing technologies.Theinstigation of completelyimprovements interms of potentiality of mobilecommunica-newwirelessbasedtechnologieswillcomplementthecurrenttionnetworks,alongwiththeinitiationofnewtypesofmobiletechnologies which are needed for the long term realizationdevices such as smart phones and tablets, have produced anof the networked society [2].2169-3536 e 2015 IEEE. Translations and content mining are permitted for academic research only.1206VOLUME3,2015Personal use is also permitted, but republication/redistribution requires IEEE permissionSeehttp://www.ieee.org/publications_standards/publications/rights/index.htmlformoreinformation
SPECIAL SECTION ON RECENT ADVANCES IN SOFTWARE DEFINED NETWORKING FOR 5G NETWORKS Received July 11, 2015, accepted July 22, 2015, date of publication July 28, 2015, date of current version August 7, 2015. Digital Object Identifier 10.1109/ACCESS.2015.2461602 A Survey of 5G Network: Architecture and Emerging Technologies AKHIL GUPTA, (Student Member, IEEE), AND RAKESH KUMAR JHA, (Senior Member, IEEE) School of Electronics and Communication Engineering, Shri Mata Vaishno Devi University, Katra 182320, India Corresponding author: A. Gupta (akhilgupta112001@gmail.com) ABSTRACT In the near future, i.e., beyond 4G, some of the prime objectives or demands that need to be addressed are increased capacity, improved data rate, decreased latency, and better quality of service. To meet these demands, drastic improvements need to be made in cellular network architecture. This paper presents the results of a detailed survey on the fifth generation (5G) cellular network architecture and some of the key emerging technologies that are helpful in improving the architecture and meeting the demands of users. In this detailed survey, the prime focus is on the 5G cellular network architecture, massive multiple input multiple output technology, and device-to-device communication (D2D). Along with this, some of the emerging technologies that are addressed in this paper include interference management, spectrum sharing with cognitive radio, ultra-dense networks, multi-radio access technology association, full duplex radios, millimeter wave solutions for 5G cellular networks, and cloud technologies for 5G radio access networks and software defined networks. In this paper, a general probable 5G cellular network architecture is proposed, which shows that D2D, small cell access points, network cloud, and the Internet of Things can be a part of 5G cellular network architecture. A detailed survey is included regarding current research projects being conducted in different countries by research groups and institutions that are working on 5G technologies. INDEX TERMS 5G, cloud, D2D, massive MIMO, mm-wave, relay, small-cell. I. INTRODUCTION Today and in the recent future, to fulfill the presumptions and challenges of the near future, the wireless based networks of today will have to advance in various ways. Recent technology constituent like high-speed packet access (HSPA) and long-term evolution (LTE) will be launched as a segment of the advancement of current wireless based technologies. Nevertheless, auxiliary components may also constitute future new wireless based technologies, which may adjunct the evolved technologies. Specimen of these new technology components are different ways of accessing spectrum and considerably higher frequency ranges, the instigation of massive antenna configurations, direct deviceto-device communication, and ultra-dense deployments [1]. Since its initiation in the late 1970s, mobile wireless communication has come across from analog voice calls to current modern technologies adept of providing high quality mobile broadband services with end-user data rates of several megabits per second over wide areas and tens, or even hundreds, of megabits per second locally. The extensive improvements in terms of potentiality of mobile communication networks, along with the initiation of new types of mobile devices such as smart phones and tablets, have produced an eruption of new applications which will be used in cases for mobile connectivity and a resultant exponential growth in network traffic. This paper presents our view on the future of wireless communication for 2020 and beyond. In this paper, we describe the key challenges that will be encountered by future wireless communication while enabling the networked society. Along with this, some technology routes that may be taken to fulfill these challenges [1]. The imagination of our future is a networked society with unbounded access to information and sharing of data which is accessible everywhere and every time for everyone and everything. To realize this imagination, new technology components need to be examined for the evolution of existing wireless based technologies. Present wireless based technologies, like the 3rd Generation Partnership Project (3GPP) LTE technology, HSPA and Wi-Fi, will be incorporating new technology components that will be helping to meet the needs of the future. Nevertheless, there may be certain scenarios that cannot be adequately addressed along with the evolution of ongoing existing technologies. The instigation of completely new wireless based technologies will complement the current technologies which are needed for the long term realization of the networked society [2]. 1206 2169-3536 2015 IEEE. Translations and content mining are permitted for academic research only. Personal use is also permitted, but republication/redistribution requires IEEE permission. See http://www.ieee.org/publications_standards/publications/rights/index.html for more information. VOLUME 3, 2015
IEEEAcceSSA. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging TechnologiesThe remainder of the paper is organized as follows:and withno security,sincevoicecalls were storedandplayedIn Section IL,we present theevolution ofwirelessin radio towers due to which vulnerability of these calls fromtechnologies.Section Ill gives the detailed description ofunwanted eavesdroppingby third party increases [7]the proposed general 5G cellular network architecture.B.2GSection IV comprises of the detailed explanation of theThe 2nd generation was introduced in late 1990's.emerging technologies for 5G wireless networks.We con-Digital technology is used in 2nd generation mobile tele-clude our paper in Section V.A list of current researchprojects based on 5G technologies is shown in the appendix.phones.Global Systems forMobile communications (GSM)was the first 2nd generation system, chiefly used for voiceII.EVOLUTIONOFWIRELESSTECHNOLOGIEScommunication and having a data rate upto64kbpsG.Marconi,an Italianinventor,unlocks thepath of2G mobile handsetbatterylasts longerbecause of the radiorecentdaywireless communicationsbycommunicatingthesignals having low power. It also provides services like Shortletter‘S'alongadistanceof 3Kmintheformof threedotMessage Service (SMS) and e-mail. Vital eminent technolo-Morse code with the help of electromagnetic waves. Aftergies were GSM, Code Division Multiple Access (CDMA),this inception,wireless communications have become anand IS-95 [3], [7].important part of present day society.Since satellite comC. 2.5Gmunication, television and radio transmission has advancedIt generally subscribes a 2nd generation cellular systemto pervasivemobiletelephone,wireless communications hastransformed thestyleinwhichsocietyruns.Theevolutionmerged with General PacketRadio Services (GPRS)andof wireless begins here [2] and is shown in Fig.1. It showsother amenities doesn'tcommonlyendow in 2G or 1Gthe evolvinggenerations of wireless technologies in terms ofnetworks.A 2.5G system generally uses 2G systemdatarate,mobility,coverageandspectralefficiency.Astheframeworks,but it applies packet switching along withwireless technologies are growing,the data rate, mobilitycircuit switching.It can assist data rate up to 144kbps. Themain 2.5Gtechnologies wereGPRS,EnhancedDataRatecoverage and spectral efficiencyincreases.It also showsthat the 1G and 2G technologies use circuit switching whilefor GSM Evolution (EDGE), and Code Division Multiple2.5Gand3Guses bothcircuitandpacketswitching andAccess (CDMA) 2000 [3], [7].the next generations from 3.5G to now i.e. 5G are usingD.3Gpacket switching.Along with these factors, it also differ-The 3rd generation was established in late 200. It impartsentiatebetween licensed spectrumandunlicensed spectrumAll the evolving generations use the licensed spectrum whiletransmission rateupto 2Mbps.Thirdgeneration (3G)the WiFi, Bluetooth and WiMAX are using the unlicensedsystems merge high speed mobile access to services basedon InternetProtocol (IP).Asidefrom transmission ratespectrum.An overviewabout theevolving wirelesstechnologies is below:unconventionalimprovementwasmadeformaintainingOosAdditional amenities like global roaming and improved voiceMobility/Coveragequality made 3G as a remarkablegeneration.The majordisadvantage for 3G handsets is that, they require morepower thanmost2Gmodels.Alongwiththis 3G networkplans are more expensive than 2G [3], [7]. SinceVehicularLicensed Spectrum73G involves the introduction and utilization of WidebandCode Division Multiple Access (WCDMA),UniversalPedestrian00Mobile Telecommunications Systems (UMTS)and CodeBEYONDGANDDivisionMultiple Access(CDMA)2000technologies,theFixedHETEROGENEOUSevolving technologies like High Speed Uplink/DownlinkNETWORKS (5G)PedestrianPacket Access (HSUPA/HSDPA)and Evolution-DataWiFi(802.1)100Optimized (EVDO)has made an intermediate wirelessotoFixedUnlicensed Spectrumgenerationbetween3Gand4Gnamedas3.5Gwith improvedData Ratedata rate of 5-30 Mbps [3]FIGURE 1.Evolution of wireless technologies.E.3.75GA.1GLong-TermEvolution technology (LTE)andFixedThe 1st generation was announced in initial 1980's.WorldwideInteroperabilityforMicrowaveAccess (WIMAX)It has a data rate up to 2.4kbps.Major subscribers wereis thefuture of mobiledata services.LTE andFixed WIMAXAdvanced Mobile Phone System (AMPS), Nordic Mobilehas thepotential to supplement the capacity of the networkTelephone(NMT),and Total Access Communicationand provides a substantial number of users the facilitytoSystem (TACS).Ithas a lot of disadvantages like belowaccess a broad range of high speed services like on demandpar capacity,reckless handoff, inferior voice associations,video, peer to peer file sharing and composite Web services.VOLUME 3, 20151207
A. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging Technologies The remainder of the paper is organized as follows: In Section II, we present the evolution of wireless technologies. Section III gives the detailed description of the proposed general 5G cellular network architecture. Section IV comprises of the detailed explanation of the emerging technologies for 5G wireless networks. We conclude our paper in Section V. A list of current research projects based on 5G technologies is shown in the appendix. II. EVOLUTION OF WIRELESS TECHNOLOGIES G. Marconi, an Italian inventor, unlocks the path of recent day wireless communications by communicating the letter ‘S’ along a distance of 3Km in the form of three dot Morse code with the help of electromagnetic waves. After this inception, wireless communications have become an important part of present day society. Since satellite communication, television and radio transmission has advanced to pervasive mobile telephone, wireless communications has transformed the style in which society runs. The evolution of wireless begins here [2] and is shown in Fig. 1. It shows the evolving generations of wireless technologies in terms of data rate, mobility, coverage and spectral efficiency. As the wireless technologies are growing, the data rate, mobility, coverage and spectral efficiency increases. It also shows that the 1G and 2G technologies use circuit switching while 2.5G and 3G uses both circuit and packet switching and the next generations from 3.5G to now i.e. 5G are using packet switching. Along with these factors, it also differentiate between licensed spectrum and unlicensed spectrum. All the evolving generations use the licensed spectrum while the WiFi, Bluetooth and WiMAX are using the unlicensed spectrum. An overview about the evolving wireless technologies is below: FIGURE 1. Evolution of wireless technologies. A. 1G The 1st generation was announced in initial 1980’s. It has a data rate up to 2.4kbps. Major subscribers were Advanced Mobile Phone System (AMPS), Nordic Mobile Telephone (NMT), and Total Access Communication System (TACS). It has a lot of disadvantages like below par capacity, reckless handoff, inferior voice associations, and with no security, since voice calls were stored and played in radio towers due to which vulnerability of these calls from unwanted eavesdropping by third party increases [7]. B. 2G The 2nd generation was introduced in late 1990’s. Digital technology is used in 2nd generation mobile telephones. Global Systems for Mobile communications (GSM) was the first 2nd generation system, chiefly used for voice communication and having a data rate up to 64kbps. 2G mobile handset battery lasts longer because of the radio signals having low power. It also provides services like Short Message Service (SMS) and e-mail. Vital eminent technologies were GSM, Code Division Multiple Access (CDMA), and IS-95 [3], [7]. C. 2.5G It generally subscribes a 2nd generation cellular system merged with General Packet Radio Services (GPRS) and other amenities doesn’t commonly endow in 2G or 1G networks. A 2.5G system generally uses 2G system frameworks, but it applies packet switching along with circuit switching. It can assist data rate up to 144kbps. The main 2.5G technologies were GPRS, Enhanced Data Rate for GSM Evolution (EDGE), and Code Division Multiple Access (CDMA) 2000 [3], [7]. D. 3G The 3rd generation was established in late 2000. It imparts transmission rate up to 2Mbps. Third generation (3G) systems merge high speed mobile access to services based on Internet Protocol (IP). Aside from transmission rate, unconventional improvement was made for maintaining QoS. Additional amenities like global roaming and improved voice quality made 3G as a remarkable generation. The major disadvantage for 3G handsets is that, they require more power than most 2G models. Along with this 3G network plans are more expensive than 2G [3], [7]. Since 3G involves the introduction and utilization of Wideband Code Division Multiple Access (WCDMA), Universal Mobile Telecommunications Systems (UMTS) and Code Division Multiple Access (CDMA) 2000 technologies, the evolving technologies like High Speed Uplink/Downlink Packet Access (HSUPA/HSDPA) and Evolution-Data Optimized (EVDO) has made an intermediate wireless generation between 3G and 4G named as 3.5G with improved data rate of 5-30 Mbps [3]. E. 3.75G Long-Term Evolution technology (LTE) and Fixed Worldwide Interoperability for Microwave Access (WIMAX) is the future of mobile data services. LTE and Fixed WIMAX has the potential to supplement the capacity of the network and provides a substantial number of users the facility to access a broad range of high speed services like on demand video, peer to peer file sharing and composite Web services. VOLUME 3, 2015 1207
IEEEAcceSSA. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging TechnologiesAlong with this, a supplementary spectrum is accessiblethewirelesssetupwhichhadcomeaboutfrom1Gto4Gwhich accredit operators manage their network very compli-Alternatively, there could be only the addition of an appli-cation or amelioration done at the fundamental network toantly and offersbetter coveragewith improved performanceforless cost [4]H7].please user requirements.This will provoke the packageproviders to drift for a 5G network as early as 4G is com-F.4Gmercially set up [8]. To meet the demands of the user and4G is generallyreferred as the descendant of the3G and 2Gto overcome the challenges that has been put forward in thestandards.3rd Generation Partnership Project (3GPP)5G system, a drastic change in the strategy of designingis presently standardizing Long Term Evolution (LTE)the 5G wireless cellular architecture is needed. A generalAdvanced asforthcoming4G standard along withMobileobservation of the researchers has shown in [14] that most ofWorldwideInteroperabilityforMicrowaveAccess(WIMAX)the wireless users stayinsideforapproximately80percent ofA4G system improves the prevailingcommunicationtime and outsidefor approximately20 percent of the time.In present wireless cellular architecture, for a mobile usernetworks by imparting acompleteandreliable solution basedon IP.Amenities like voice,data and multimedia will beto communicate whether inside or outside, an outside basestation present in the middle of a cell helps incommunication.imparted to subscribers on every time and everywhere basisand at quite higher data rates as related to earlier generations.So for inside usersto communicate with the outside baseApplicationsthat are beingmadetouse a 4Gnetwork arestation, the signals will have to travel through the walls ofMultimedia Messaging Service (MMS),Digital Videothe indoors, and this will result in very high penetration lossBroadcasting (DVB), and video chat, High Definition TVwhichcorrespondinglycosts with reduced spectral efficiency,data rate,and energyefficiency ofwireless communications.content and mobile TV [2], [4]H6].To overcome this challenge, a new idea or designing tech-G.5Gnique that has come in to existence for scheming the5G cellular architecture is to distinct outside and insideWith an exponential increase in the demand of the userssetups [8].With this designing technique, the penetration loss4G will now be easily replaced with 5G withanthrough the walls of the building will be slightly reduced.advanced access technology named Beam Division MultipleThis idea will be supported with the help of massive MIMOAccess (BDMA)and Non-and quasi-orthogonal or FilterBank multi carrier (FBMC) multiple access. The concepttechnology [15], in which geographically dispersed arrayof antenna's are deployed which have tens or hundreds ofbehind BDMAtechniqueisexplainedby considering the caseantennaunits.SincepresentMIMOsystemsareusingeitherofthebasestationcommunicatingwiththemobilestations.twoorfour antennas,buttheideaofmassiveMIMO systemsIn this communication,an orthogonal beamisallocated toeachmobile station and BDMAtechnique will divide thathas come up with the idea of utilizing theadvantages of largearray antenna elements in terms of huge capacity gains.antenna beam accordingto locations of themobile stationsTo build or construct a largemassive MIMO network,for giving multiple accesses to themobile stations, whichfirstly the outside base stations will be fitted with largecorrespondingly increase the capacity of the system [8].An idea to shift towards 5G is based on current drifts,it isantenna arrays and among them some are dispersed aroundthe hexagonal cell and linked to the base station throughcommonly assumed that5G cellularnetworks mustaddressoptical fibercables,aidedwithmassiveMIMOtechnologiessix challenges that are not effectively addressed by 4G ie.higher capacity, higher data rate, lower End to End latency.The mobile users present outside are usually fitted with acertain number of antenna units but with cooperation a largemassive device connectivity,reduced cost and consistentQuality of Experience provisioning [22], [23]. Thesevirtualantennaarraycanbeconstructed,whichtogetherwithantenna arrays of base station formvirtual massive MIMOchallenges are concisely shown in Fig. 2 along withlinks.Secondly,every building will be installed with largesome potential facilitators to address them. An overviewantenna arraysfrom outside,tocommunicate with outdoorof the challenges,facilitators, and corresponding designbase stations with the help of line of sight componentsfundamentals for 5G is shown in Fig.2 [20].RecentlyThe wireless access points inside the building are connectedintroduced IEEE 802.11ac,802.11ad and 802.11af standardswith the large antenna arrays through cables for communi-are very helpful and act as a building blocks in the roadcating with indoor users. This will significantly improvestowards5G[9]H13].Thetechnicalcomparisonbetween thesethe energy efficiency,cell average throughput, data rate, andstandards is shown in table 1 and the detailed comparison ofspectral efficiency of the cellular system but at the expensewireless generations is shown intable2of increased infrastructure cost.With the introduction ofIIL5GCELLULARNETWORKARCHITECTUREsuch an architecture, the inside users will only have toTo contemplate5G network in the market now,it is evidentconnect or communicate with inside wireless access pointsthat the multiple access techniques in the network arewhile larger antenna arays remained installed outside thealmost at a still and requires sudden improvement.Currentbuildings[8].For indoor communication,certain technolo-technologies like OFDMA will work at least for nextgies like WiFi, Small cell, ultra wideband,millimeter wave50 years. Moreover, there is no need to have a change incommunications [16], and visible light communications [17]1208VOLUME 3,2015
A. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging Technologies Along with this, a supplementary spectrum is accessible which accredit operators manage their network very compliantly and offers better coverage with improved performance for less cost [4]–[7]. F. 4G 4G is generally referred as the descendant of the 3G and 2G standards. 3rd Generation Partnership Project (3GPP) is presently standardizing Long Term Evolution (LTE) Advanced as forthcoming 4G standard along with Mobile Worldwide Interoperability for Microwave Access (WIMAX). A 4G system improves the prevailing communication networks by imparting a complete and reliable solution based on IP. Amenities like voice, data and multimedia will be imparted to subscribers on every time and everywhere basis and at quite higher data rates as related to earlier generations. Applications that are being made to use a 4G network are Multimedia Messaging Service (MMS), Digital Video Broadcasting (DVB), and video chat, High Definition TV content and mobile TV [2], [4]–[6]. G. 5G With an exponential increase in the demand of the users, 4G will now be easily replaced with 5G with an advanced access technology named Beam Division Multiple Access (BDMA) and Non- and quasi-orthogonal or Filter Bank multi carrier (FBMC) multiple access. The concept behind BDMA technique is explained by considering the case of the base station communicating with the mobile stations. In this communication, an orthogonal beam is allocated to each mobile station and BDMA technique will divide that antenna beam according to locations of the mobile stations for giving multiple accesses to the mobile stations, which correspondingly increase the capacity of the system [8]. An idea to shift towards 5G is based on current drifts, it is commonly assumed that 5G cellular networks must address six challenges that are not effectively addressed by 4G i.e. higher capacity, higher data rate, lower End to End latency, massive device connectivity, reduced cost and consistent Quality of Experience provisioning [22], [23]. These challenges are concisely shown in Fig. 2 along with some potential facilitators to address them. An overview of the challenges, facilitators, and corresponding design fundamentals for 5G is shown in Fig. 2 [20]. Recently introduced IEEE 802.11ac, 802.11ad and 802.11af standards are very helpful and act as a building blocks in the road towards 5G [9]–[13]. The technical comparison between these standards is shown in table 1 and the detailed comparison of wireless generations is shown in table 2. III. 5G CELLULAR NETWORK ARCHITECTURE To contemplate 5G network in the market now, it is evident that the multiple access techniques in the network are almost at a still and requires sudden improvement. Current technologies like OFDMA will work at least for next 50 years. Moreover, there is no need to have a change in the wireless setup which had come about from 1G to 4G. Alternatively, there could be only the addition of an application or amelioration done at the fundamental network to please user requirements. This will provoke the package providers to drift for a 5G network as early as 4G is commercially set up [8]. To meet the demands of the user and to overcome the challenges that has been put forward in the 5G system, a drastic change in the strategy of designing the 5G wireless cellular architecture is needed. A general observation of the researchers has shown in [14] that most of the wireless users stay inside for approximately 80 percent of time and outside for approximately 20 percent of the time. In present wireless cellular architecture, for a mobile user to communicate whether inside or outside, an outside base station present in the middle of a cell helps in communication. So for inside users to communicate with the outside base station, the signals will have to travel through the walls of the indoors, and this will result in very high penetration loss, which correspondingly costs with reduced spectral efficiency, data rate, and energy efficiency of wireless communications. To overcome this challenge, a new idea or designing technique that has come in to existence for scheming the 5G cellular architecture is to distinct outside and inside setups [8]. With this designing technique, the penetration loss through the walls of the building will be slightly reduced. This idea will be supported with the help of massive MIMO technology [15], in which geographically dispersed array of antenna’s are deployed which have tens or hundreds of antenna units. Since present MIMO systems are using either two or four antennas, but the idea of massive MIMO systems has come up with the idea of utilizing the advantages of large array antenna elements in terms of huge capacity gains. To build or construct a large massive MIMO network, firstly the outside base stations will be fitted with large antenna arrays and among them some are dispersed around the hexagonal cell and linked to the base station through optical fiber cables, aided with massive MIMO technologies. The mobile users present outside are usually fitted with a certain number of antenna units but with cooperation a large virtual antenna array can be constructed, which together with antenna arrays of base station form virtual massive MIMO links. Secondly, every building will be installed with large antenna arrays from outside, to communicate with outdoor base stations with the help of line of sight components. The wireless access points inside the building are connected with the large antenna arrays through cables for communicating with indoor users. This will significantly improves the energy efficiency, cell average throughput, data rate, and spectral efficiency of the cellular system but at the expense of increased infrastructure cost. With the introduction of such an architecture, the inside users will only have to connect or communicate with inside wireless access points while larger antenna arrays remained installed outside the buildings [8]. For indoor communication, certain technologies like WiFi, Small cell, ultra wideband, millimeter wave communications [16], and visible light communications [17] 1208 VOLUME 3, 2015
IEEEAcceSSA. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging TechnologiesFacilitators to address challenges5GdesignfundamentalsChallengesSpectrumUse high freguencies andotherspectrumoptionslikeMassive MIMOpooling and aggregation.NewairinterfacesandCapacityNewairinterfacemultiple access schemes candesignedprovidebe1Ox1000Allopticaloptimized high frequencies>70%indo0rnetworkslatencyandmassiveconnectivitySmall cellsData RateOpticaltransmission andswitchingwhereverpossiblex10-100Local offloadBring communicatingContent DeliveringEndtoEnd latencyendpoints closertogetherNetwork(CDN)Addressandcoverage<5msControl/User-planecapacity separatelysplitMassive number ofSoftware basedMinimizenumberOconnectionsapproachesnetworklayersandpoOmuchesourcesasUserdeploymentpossible using cloud.x10-100modelsMinimize functionalitieseaccessSimpleCostperformedbyaccesspoints.pointsEnergyefficientSustainablehardwareMaximize energy efficiencyEnergyOualityofacrossallnetworkentitiesmanagementExperience(QoE)techniquesSelf OrganizingConsistentUseanintelligentagenttoNetworks(SON)manage OoE,routingmobilityand resourceTrafficallocationmanagementBig data-drivennetworkintelligenceFIGURE 2. 5G challenge, facilitators, and design fundamental [20].areuseful for small rangecommunications having largedataconventionallyused for cellular communications.But it isrates.Buttechnologies like millimeter wave and visible lightnot an efficient idea to use these high frequency waves forcommunicationareutilizinghigherfrequencieswhicharenotoutsideand longdistanceapplicationsbecausethesewaves1209VOLUME 3, 2015
A. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging Technologies FIGURE 2. 5G challenge, facilitators, and design fundamental [20]. are useful for small range communications having large data rates. But technologies like millimeter wave and visible light communication are utilizing higher frequencies which are not conventionally used for cellular communications. But it is not an efficient idea to use these high frequency waves for outside and long distance applications because these waves VOLUME 3, 2015 1209
IEEEAcceSSA. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging TechnologiesTABLE 1.Technical comparison between recent 802.11 standards.Technical Specifications802.11an802.11ac802.11ad802.11af2.4,4.9, 5GHz5GHz60 GHzFrequency0.47-0.71 GHzModulation schemeOFDMOFDMOFDM, single carrier,OFDMlow-power singlecarrier20,40 MHz5,10, 20, 40Channel bandwidth20, 40, 80 MHz (160 MHz optional)2 GHzMHzUp to 150 Mbps (1xl, 40 MHz)Up to 433 Mbps (IxI, 80 MHz)4.6 Gbps54MbpsNominal data rate, single streamUp to 867 Mbps (1x1. 160 MHz)Up to 600 Mbps (4x4, 40 MHz)Up to 1.73 Gbps (4x4, 80 MHz)7 GbpsAggregate nominal data rate,multiple streamsUp to 3.47 Gbps (4x4, 160 MHz)Spectral Efficiency21.665 bps/Hz (4x4, 80 MHz)NA15 bps/Hz (4x4, 40 MHz)1 bps/Hz (2GHz)EIRP22-29dBm1-10dBm22-36 dBm16-20 dBmRange12-70 m indoor12-35 m indoor60 m indoor, 100m<100m indooroutdoor<5kmoutdoorYYAYThrough WallsYYNon-Line-of-Sight4YYWorld-Wide AvailabilityYY (Limited in china)will not infiltrate from dense materials efficiently and canControl plane, respectively. Special network functionality aseasily be dispersed by rain droplets, gases, and flora. Though,a service (XaaS)will provide service as per need, resourcemillimeterwaves andvisiblelightcommunicationstechnolo-pooling is one of the examples.Xaas is the connectiongies can enhance the transmission data rate for indoor setupsbetween aradionetwork and a networkcloud [20].The5Gcellularnetwork architecture is explainedbecausethey have come upwithlarge bandwidth.Alongwith the introduction of new spectrum,which is not beingin [8] and [20].It has equal importance in terms of frontconventionally usedfor wireless communication,thereis oneend and backhaul network respectively. In this paper, amore method to solve the spectrum shortage problem bygeneral 5G cellular network architecture has been proposedimprovingthe spectrum utilization of current radio spectraas shown in Fig. 3. It describes the interconnectivitythrough cognitive radio (CR) networks [18].among the different emerging technologies like MassiveSince the 5G cellular architecture is heterogeneous, so itMIMO network,Cognitive Radio network,mobile andmust include macrocells,microcells, small cells,and relays.static small-cell networks.This proposed architecture alsoAmobilesmall cell concept is an integral part of 5G wirelessexplains the role of network function virtualization (NFV)cellular networkand partially comprisesof mobilerelayandcloud in the 5G cellular network architecture.The conceptsmall cell concepts [19]. It is being introduced to put upofDevicetoDevice(D2D)communication,small cellaccesshigh mobility users,which are inside the automobiles andpoints and Internet of things (loT)has alsobeen incorporatedhigh speedtrains.Mobile small cells arepositioned insidethein this proposed 5G cellular network architecture. In general,moving automobiles to communicate with the users insidethis proposed 5G cellular network architecture mayprovidethe automobile, while the massive MIMO unit consistingagood platformforfuture5G standardization network.of large antennaarrays is placed outsidethe automobiletoBut there are several issues that need to be addressed incommunicate with the outside base station.According toorder to realize the wireless network architecture in partic-user's opinion, a mobile small cell is realized as a regularular, and 5G networks in general. Some of these issues aresummarized in Table. 3 [20].base station and itsallied users are all observed asa singleunit to the base station which proves the above idea ofIV.EMERGINGTECHNOLOGIESFORsplitting indoor and outdoor setups.Mobile small cellusers [19] have a high data rate for data rate services with5GWIRELESS NETWORKSconsiderably reduced signaling overhead, as shown in [8]It is expected that mobile and wireless traffic volume willAs the 5G wireless cellular network architecture consistsincrease a thousand-fold over the next decade which willof only two logical layers: a radio network and a networkbe driven by the expected 50 billion connected devices con-cloud.Different types of componentsperforming differentnected to the cloud by2020 and all need to access and sharefunctions are constituting theradio network.The networkdata, anywhere and anytime.With a rapid increase in the numfunction virtualization (NFV) cloud consists of a User planeber of connected devices,some challengesappear which willentity (UPE)and a Control plane entity (CPE)that per-be responded by increasing capacity and by improving energyform higher layer functionalities related to the User andefficiency,costandspectrumutilizationas well as providing1210VOLUME 3,2015
A. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging Technologies TABLE 1. Technical comparison between recent 802.11 standards. will not infiltrate from dense materials efficiently and can easily be dispersed by rain droplets, gases, and flora. Though, millimeter waves and visible light communications technologies can enhance the transmission data rate for indoor setups because they have come up with large bandwidth. Along with the introduction of new spectrum, which is not being conventionally used for wireless communication, there is one more method to solve the spectrum shortage problem by improving the spectrum utilization of current radio spectra through cognitive radio (CR) networks [18]. Since the 5G cellular architecture is heterogeneous, so it must include macrocells, microcells, small cells, and relays. A mobile small cell concept is an integral part of 5G wireless cellular network and partially comprises of mobile relay and small cell concepts [19]. It is being introduced to put up high mobility users, which are inside the automobiles and high speed trains. Mobile small cells are positioned inside the moving automobiles to communicate with the users inside the automobile, while the massive MIMO unit consisting of large antenna arrays is placed outside the automobile to communicate with the outside base station. According to user’s opinion, a mobile small cell is realized as a regular base station and its allied users are all observed as a single unit to the base station which proves the above idea of splitting indoor and outdoor setups. Mobile small cell users [19] have a high data rate for data rate services with considerably reduced signaling overhead, as shown in [8]. As the 5G wireless cellular network architecture consists of only two logical layers: a radio network and a network cloud. Different types of components performing different functions are constituting the radio network. The network function virtualization (NFV) cloud consists of a User plane entity (UPE) and a Control plane entity (CPE) that perform higher layer functionalities related to the User and Control plane, respectively. Special network functionality as a service (XaaS) will provide service as per need, resource pooling is one of the examples. XaaS is the connection between a radio network and a network cloud [20]. The 5G cellular network architecture is explained in [8] and [20]. It has equal importance in terms of front end and backhaul network respectively. In this paper, a general 5G cellular network architecture has been proposed as shown in Fig. 3. It describes the interconnectivity among the different emerging technologies like Massive MIMO network, Cognitive Radio network, mobile and static small-cell networks. This proposed architecture also explains the role of network function virtualization (NFV) cloud in the 5G cellular network architecture. The concept of Device to Device (D2D) communication, small cell access points and Internet of things (IoT) has also been incorporated in this proposed 5G cellular network architecture. In general, this proposed 5G cellular network architecture may provide a good platform for future 5G standardization network. But there are several issues that need to be addressed in order to realize the wireless network architecture in particular, and 5G networks in general. Some of these issues are summarized in Table. 3 [20]. IV. EMERGING TECHNOLOGIES FOR 5G WIRELESS NETWORKS It is expected that mobile and wireless traffic volume will increase a thousand-fold over the next decade which will be driven by the expected 50 billion connected devices connected to the cloud by 2020 and all need to access and share data, anywhere and anytime. With a rapid increase in the number of connected devices, some challenges appear which will be responded by increasing capacity and by improving energy efficiency, cost and spectrum utilization as well as providing 1210 VOLUME 3, 2015
IEEEAcceSSA. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging TechnologiesTABLE 2.Evolution of wireless technologies.GenerationsAccess TechnologyData RateFrequencyBandwidthForwardSwitchingApplicationsBandErrorCorrection1GAdvanced Mobile Phone Service (AMPS)2.4 kbps800 MHz30 KHzNAVoiceCircuit(Frequency Division Multiple Access(FDMA)2GGlobal Systems for Mobile communications10kbps850/900/180200KHzNACircuitVoice +Data(GSM) (Time Division Multiple Access0/1900MHz(TDMA))Code Division Multiple Access (CDMA)10 kbps1.25 MHz2.5G200KHzCircuit/ General Packet Radio Service (GPRS)50 kbpsPacketEnhanced Data Rate for GSM Evolution200 kbps200 KHz(EDGE)3GWideband Code Division Multiple Access800/850/900/5MHzCircuivVoice+ Data384kbpsTurbo Codes(WCDMA) / Universal Mobile1800/1900/Packet+ VideoTelecommunications Systems (UMTS)2100MHzcalling1.25 MHzCircuit/Code Division Multiple Access (CDMA) 2000384kbpsPacket3.5GHigh Speed Uplink / Downlink Packet Access5-30 Mbps5MHzPacket(HSUPA/HSDPA)Evolution-Data Optimized (EVDO)5-30 Mbps1.25 MHzPacket3.75G100-2001.8GHz,1.4MHz toPacketOnlineLong Term Evolution (LTE) (Orthogonal /ConcatenatedMbps2.6GHz20 MHzSingle Carrier Frequency Division Multiplecodesgaming+HighAccess) (OFDMA/SC-FDMA)DefinitionTelevisionWorldwide Interoperability forFixed100-2003.5GHz and3.5MHzMicrowaveAccessWIMAXMbps5.8GHzand 7MHz(WIMAX)(Scalablein3.5GHzinitiallyband;Orthogonal Frequency10MHz inDivision Multiple5.8GHzAccess(SOFDMA)band4GDL3Gbps1.8GHz.1.4MHz toPacketOnlineLong Term Evolution Advanced (LTE-A)Turbo codes(Orthogonal / Single Carrier FrequencyUL1.5Gbps2.6GHz20 MHzgaming+HighDivision Multiple Access) (OFDMA/ SC-FDMA)DefinitionMobile100-2002.3GHz,3.5MHz.TelevisionWorldwide Interoperability forWIMAXMbps2.5GHz,and7MHz,Microwave Access3.5GHz5MHz,(WIMAX)(Scalable initially10MHz,Orthogonal FrequencyandDivision Multiple8.75MHzAccess(SOFDMA)initially5GUltra HighBeam Division Multiple Access (BDMA) and10-50 Gbps1.8, 2.6 GHz60GHzLow DensityPacketNon- and quasi-orthogonal or Filter Bank multiParity Checkdefinition(expected)and expected30-300 GHzCodesvideo +carrier (FBMC) multiple access(LDPC)VirtualRealityapplicationsbetter scalability forhandling the increasing number of theof applications and requirements of the user.Toprovideaconnected devices.For the vision of all-communicating worldcommonconnectedplatformforavarietyofapplicationsandrelativetotodaysnetwork,theoverall technical aimis torequirementsfor5G,wewill researchthebelowtechnologyprovide a system idea that supports [21]:components[21];.1000 times increased data volume per area.Radio-links,includes the development of new transmis-10to100timesincreasednumberofconnecteddevicession waveforms andnewapproaches of multipleaccess.10to100times increasedtypical user data ratecontrol and radio resource management..10times extendedbattery lifeforlowpowerMassive.Multi-nodeandmulti-antennatransmissions,includesMachineCommunication(MMC)devicesdesigning ofmulti-antenna transmission/reception tech-5 times reduced End-to-End (E2E) latency·nologies based on massive antenna configurations andIn this paper, we will cover a wide area of technologiesdeveloping advanced inter-node coordination schemeswith a lot of technical challenges arises due to a varietyand multi-hop technologies.1211VOLUME 3, 2015
A. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging Technologies TABLE 2. Evolution of wireless technologies. better scalability for handling the increasing number of the connected devices. For the vision of all-communicating world relative to today’s network, the overall technical aim is to provide a system idea that supports [21]: • 1000 times increased data volume per area • 10 to 100 times increased number of connected devices • 10 to 100 times increased typical user data rate • 10 times extended battery life for low power Massive Machine Communication (MMC) devices • 5 times reduced End-to-End (E2E) latency In this paper, we will cover a wide area of technologies with a lot of technical challenges arises due to a variety of applications and requirements of the user. To provide a common connected platform for a variety of applications and requirements for 5G, we will research the below technology components [21]: • Radio-links, includes the development of new transmission waveforms and new approaches of multiple access control and radio resource management. • Multi-node and multi-antenna transmissions, includes designing of multi-antenna transmission/reception technologies based on massive antenna configurations and developing advanced inter-node coordination schemes and multi-hop technologies. VOLUME 3, 2015 1211
IEEEAcCeSSA. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging TechnologiesNTERNEWIREDLINKMASSIVE MIMO LINKSWIRELESSLINKSNFVenabledNWCISOURCELINKTFSRELAYCONTROLPLANECOMMUNICATIONANINTERNEIXOMMUNICAT#CR-Cognitive RadicVLC-Visible Light CommuatirLOS-Line of SightSERVERMIMOMutliple Input Multiple OuputETWORSCPE-Control Plane EntityUPE-User Plane EnttyNI-NetwTntellieNFV-NAFKMWNMASSIVEMIMCalitiesas a SeriNETWORKD2D-Device to Device ComtaniatoINTERNETSMALL CELNETWORINERNETWIRELESS SENSORNETWORKSNTERNET4COMPUTATIONALDEVICI欢GIGABITETHERNEInternet ofThings (loT)FIGURE 3.A general 5G cellular network architecture..Network dimension, includes considering the demand,In this section, we identify several technologies, ranked intraffic and mobility management, and novel approachesperceived importance, which will be crucial in future wirelessfor efficient interference management in complexstandards.heterogeneousdeployments.A.MASSIVEMIMOSpectrumusage,includesconsideringextendedMassive MIMO is an evolving technology that has beenspectrum band ofoperation,as wellas operation in newupgraded from the current MIMO technology. The Massivespectrum regimes to provide a complete system conceptfor new spectrum regimes that carefully addresses theMIMO systemuses arrays of antenna containingfewhundredneeds ofeachusagescenario.antennas which are at the same time in one time, frequencyNow the topics which will integrate a subset of theslot serving many tens of user terminals.The main objectivetechnologycomponentsandprovidesthesolutionof someofof MassiveMIMO technology is to extract all thebenefitsthe goals which are identified earlier are [21]:of MIMObut on a larger scale.Ingeneral,massiveMIMO.Device-to-Device (D2D) communications refers tois an evolving technology of Next generation networks,directcommunication between devices allowinglocalwhich is energyefficient,robust,and secureand spectrumexchange of user plane traffic without going through aefficient [24]MassiveMIMO depends on spatial multiplexing,whichnetworkinfrastructure.MassiveMachineCommunications(MMC)willformfurther depends on the base station to have channel statethe basis of the Internet of Things with a wide rangeinformation, both on the uplink as well as on the downlink.of application fields including theautomotive industry,In case of downlink, it is not easy,but in case of uplink,publicsafety,emergencyservicesandmedicalit is easy,as the terminals send pilots. On thebasis offield.pilots, the channel response of each terminal is estimated..Moving Networks (MN)will enhance and extendIn conventionalMIMOsystems,thebase station sendsthelinking together potentially large populations of jointlypilot waveforms to the terminals and based on these, themovingcommunicationdevices.terminal estimatethechannel,quantizeitandfeedbackthem.Ultra-dense Networks (UDN)will be the main driverto the base station.This process is not viable for mas-siveMIMO systems,especially in high mobility conditionswhose goals are to increase capacity,increase energyefficiencyof radio links, and enablebetter exploitationbecause of two reasons.Firstly thedownlink pilots from theof under-utilized spectrum.base station must be orthogonal among the antennas, dueUltra-reliable Networks (URN) will enable highto which the requirement of time, frequency slots for thedegrees of availabilitydownlink pilots increases with theincrease in the number1212VOLUME 3,2015
A. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging Technologies FIGURE 3. A general 5G cellular network architecture. • Network dimension, includes considering the demand, traffic and mobility management, and novel approaches for efficient interference management in complex heterogeneous deployments. • Spectrum usage, includes considering extended spectrum band of operation, as well as operation in new spectrum regimes to provide a complete system concept for new spectrum regimes that carefully addresses the needs of each usage scenario. Now the topics which will integrate a subset of the technology components and provides the solution of some of the goals which are identified earlier are [21]: • Device-to-Device (D2D) communications refers to direct communication between devices allowing local exchange of user plane traffic without going through a network infrastructure. • Massive Machine Communications (MMC) will form the basis of the Internet of Things with a wide range of application fields including the automotive industry, public safety, emergency services and medical field. • Moving Networks (MN) will enhance and extend linking together potentially large populations of jointly moving communication devices. • Ultra-dense Networks (UDN) will be the main driver whose goals are to increase capacity, increase energy efficiency of radio links, and enable better exploitation of under-utilized spectrum. • Ultra-reliable Networks (URN) will enable high degrees of availability. In this section, we identify several technologies, ranked in perceived importance, which will be crucial in future wireless standards. A. MASSIVE MIMO Massive MIMO is an evolving technology that has been upgraded from the current MIMO technology. The Massive MIMO system uses arrays of antenna containing few hundred antennas which are at the same time in one time, frequency slot serving many tens of user terminals. The main objective of Massive MIMO technology is to extract all the benefits of MIMO but on a larger scale. In general, massive MIMO is an evolving technology of Next generation networks, which is energy efficient, robust, and secure and spectrum efficient [24]. Massive MIMO depends on spatial multiplexing, which further depends on the base station to have channel state information, both on the uplink as well as on the downlink. In case of downlink, it is not easy, but in case of uplink, it is easy, as the terminals send pilots. On the basis of pilots, the channel response of each terminal is estimated. In conventional MIMO systems, the base station sends the pilot waveforms to the terminals and based on these, the terminal estimate the channel, quantize it and feedback them to the base station. This process is not viable for massive MIMO systems, especially in high mobility conditions because of two reasons. Firstly the downlink pilots from the base station must be orthogonal among the antennas, due to which the requirement of time, frequency slots for the downlink pilots increases with the increase in the number 1212 VOLUME 3, 2015
IEEEACCeSSA. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging TechnologiesTABLE 3.Small cell setup options and concern [20].User-setupOperator-setupLicensedPositivesPositivesSpectrumOperatorcontrolled CellsitesReduced cost based on equipment, setup and operationEasier to provide Quality of experienceNegativesRealization of advanced resource allocationFor later service customer sustenance, added operational cost is required(RA) techniques tum out to be easierConcernNegativesMonitoring issuesIncreased cost based on equipment. setup andPublic or private access controloperationEnsuring Quality of experienceLimited spectrumEffect of various backhaul types on advanced resource allocation techniquesSpectrum license feesProvisioning of over the air securityConcernBackhaul provisioning-UnlicensedPositivesPositivesspectrumOperatorcontrolled Cell sitesReduced costbasedon equipment.setupandoperationOperators have extra spectrum for exploitationNegativesLack of Quality of experience agreementsNegativesIncreased cost based on equipment, setup andConcernoperationAccesscontrolLack of Quality of experience agreementsMechanisms to guarantee impartial performanceConcurrence with Wi-Fi, Bluctooth, etce.ConcernMechanisms to guarantee impartialEffect of various backhaul types on advanced resource allocation techniquesperformanceProvisioning of over-the-air securityConcurrence with Wi-Fi, Bluctooth, cte.Backhaul provisioningof antennas.So Massive MIMO systems would now requireplay by confirming that all the wave fronts that have beena large number of similar slots as compared to the con-emittedfrom theantennas possiblywill add constructivelyatventional MIMO system. Secondly,as the number of basethe intended terminal's locations and destructively elsewherestation antennas increases the number of the channel esti-Zero forcing is used to suppress the remaining interfer-mates also increases for each terminal which in turn neededencebetween theterminals,but atthe expense of increasedhundred times more uplink slots to feedback the channeltransmitted power [24].responses to thebase station.A general solution to this prob-Thedesirability of maximumratio combining(MRC)islem is to work in Time Division Duplexing (TDD) modemore as relatedto Zero forcing (ZF)because of its com-and depend on the reciprocity amid the uplink and downlinkputational ease i.e. received signals are multiplied by theirchannels [25]conjugate channel responses and due to the reason that it isMassiveMIMO technologydepends onphase coherentexecuted in adispersed mode,autonomouslyateveryantennasignals from all the antennas at the base station, but theelement.Though ZF also works equally well for an orthodoxcomputational processing of these signals is simple.BelowMIMO systemwhichMRC normally doesnot.Themainarecertain positives ofa massive MIMO system [24]:reason behind the efficient use of the MRC with massiveMIMO involving largenumberof base station antennas,the1)MASSIVEMIMOHASTHECAPABILITYTHATITCANchannel responses allied with different terminals tend to beIMPROVETHERADIATEDENERGYEFFICIENCYBYalmost orthogonal.100TIMESANDATTHESAMETIME,INCREASESWith the use of MRC receiver, we are operating in aTHECAPACITYOFTHEORDEROF1OORMOREnoise restricted system.MRC in MassiveMIMO systemThe positive of increase in capacity is because of thewill scaledown thepowerto an extentpossibledeprived ofMassivespatialmultiplexingtechniqueusedinreally upsetting the overall spectral efficiency and multiuserMIMO systems.Regarding the improvement in theradiatedinterference, but the effects of hardware deficiencies areenergy efficiency, it is because of the increase in the numberlikelytobe overcomebythe thermal noise.But the intentionof antennas,theenergy can nowbeconcentrated in smallbehind the overall 10 times higher spectral efficiency asregions in the space. It is based on the principle of coherentcomparedto conventional MIMOisbecause10timesmoresuperposition of wave fronts. After transmitting the shapedterminals are served concurrently in the same time frequencysignals from the antennas, the base station has no role toresource[26].1213VOLUME3,2015
A. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging Technologies TABLE 3. Small cell setup options and concern [20]. of antennas. So Massive MIMO systems would now require a large number of similar slots as compared to the conventional MIMO system. Secondly, as the number of base station antennas increases the number of the channel estimates also increases for each terminal which in turn needed hundred times more uplink slots to feedback the channel responses to the base station. A general solution to this problem is to work in Time Division Duplexing (TDD) mode and depend on the reciprocity amid the uplink and downlink channels [25]. Massive MIMO technology depends on phase coherent signals from all the antennas at the base station, but the computational processing of these signals is simple. Below are certain positives of a massive MIMO system [24]: 1) MASSIVE MIMO HAS THE CAPABILITY THAT IT CAN IMPROVE THE RADIATED ENERGY EFFICIENCY BY 100 TIMES AND AT THE SAME TIME, INCREASES THE CAPACITY OF THE ORDER OF 10 OR MORE The positive of increase in capacity is because of the spatial multiplexing technique used in Massive MIMO systems. Regarding the improvement in the radiated energy efficiency, it is because of the increase in the number of antennas, the energy can now be concentrated in small regions in the space. It is based on the principle of coherent superposition of wave fronts. After transmitting the shaped signals from the antennas, the base station has no role to play by confirming that all the wave fronts that have been emitted from the antennas possibly will add constructively at the intended terminal’s locations and destructively elsewhere. Zero forcing is used to suppress the remaining interference between the terminals, but at the expense of increased transmitted power [24]. The desirability of maximum ratio combining (MRC) is more as related to Zero forcing (ZF) because of its computational ease i.e. received signals are multiplied by their conjugate channel responses and due to the reason that it is executed in a dispersed mode, autonomously at every antenna element. Though ZF also works equally well for an orthodox MIMO system which MRC normally does not. The main reason behind the efficient use of the MRC with massive MIMO involving large number of base station antennas, the channel responses allied with different terminals tend to be almost orthogonal. With the use of MRC receiver, we are operating in a noise restricted system. MRC in Massive MIMO system will scale down the power to an extent possible deprived of really upsetting the overall spectral efficiency and multiuser interference, but the effects of hardware deficiencies are likely to be overcome by the thermal noise. But the intention behind the overall 10 times higher spectral efficiency as compared to conventional MIMO is because 10 times more terminals are served concurrently in the same time frequency resource [26]. VOLUME 3, 2015 1213
IEEEAcCeSSA. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging Technologies2)MASSIVEMIMOSYSTEMSCANBEPUTTOGETHERit is helpful to deploy base stations to the places whereWITHTHEHELPOFLOWPOWERANDelectricity is not available. Along with this,the increasedLESSCOSTLYCOMPONENTSconcerns of electromagnetic exposure will be considerablyless.Massive MIMO hascome upwitha change withrespect to concept,schemes and execution.Massive3)MASSIVEMIMOPERMITSASUBSTANTIALDECREASEMIMOsystems usehundreds of less expensiveamplifiers inINLATENCYONTHEAIRINTERFACErespect to expensive ultra-linear50Watt amplifiers becauseearlier are having an output power in the milliwatt range,Latency is the prime area of concern in the next generationwhich is much better than the latter which are generallynetworks.In wireless communication,the main cause ofbeing usedinconventionalsystems.Itisdissimilartocon-latencyisfading.This phenomenon occurs amid the baseventional array schemes,as itwill useonlyalittle antenna'sstationandterminal,i.e.whenthe signalistransmittedfromthat are beingfed from high power amplifiers but having athe base station, it travels through different multiple pathsnotable impact.The most significant improvement is aboutbecause ofthe phenomenon's like scattering,reflection andtheremoval ofa largenumberofexpensiveandmassiveitemsdiffraction before it reaches the terminal. When the signallike large coaxial cables [24].through these multiple paths reaches the terminal it will inter-With the use of a large number of antennas in massivefereeither constructively or destructively,and the case whenMIMO technology the noise,fading and hardware deficitsfollowing waves from these multiple paths interfere destrucwill be averaged because signals from a large number oftively,thereceived signal strengthreducestoaconsiderableantennas are combinedtogetherin thefree space.Itcondenseslow point.If theterminal is caught in a fading dip,then it hasthe limits on precision and linearity of every single amplifiertowaitforthetransmissionchanneltochangeuntilanydataand radio frequency chain and altogether what matters iscan be received.Massive MIMO,due to a large number oftheir collective action. This will increase the robustness ofantennas and with the idea of beam forming can avoid fadingmassive MIMO against fading and failure of one of thedips and now latency cannot befurtherdecreased [24].antennaelements.Amassive MIMO systemhas degrees of freedom in excess.4)MASSIVEMIMOMAKESTHEMULTIPLEFor example,with 100 antennas,10terminals areshowingACCESSLAYERSIMPLEpresence while the remaining 90 degrees of freedom areWith the arrival of Massive MIMO, the channel strengthstill available.These available degrees of freedom can beens and now frequency domain scheduling is not enoughexploited by using them for signal shaping which will beOFDMprovides,each subcarrier in a massive MIMO systemhardware friendly.Specifically,each antenna with the use ofwithconsiderablythesamechannelgaindueto whicheachvery cheap andpowerproficientradiofrequencyamplifiersandeveryterminalcanbeprovidedwithcompletebandwidthcan transmit signals having small peak to average ratio [27]which reduces most of the physical layer control signalingandconstantenvelope[28] ata modestpriceofincreasedtotalterminated [24]radiated power.With the help of constant envelopemultiuser5)MASSIVEMIMOINCREASESTHESTRENGTHEQUALLYprecoding,the signals transmitted from each antenna areAGAINSTUNINTENDEDMANMADEINTERFERENCEneither being formed in terms of beam nor by weighing ofANDINTENDEDJAMMINGa symbol. Rather, a wave field is created and sampled withrespect to the locationof the terminals and they can seeJammingof the wirelesssystems of the civilian is aprecisely the signals what we intended to make them see.prime area of concern and poses a serious threat to cyberMassive MIMO has a vital property which makes it possible.security.Owing to limited bandwidth, the distribution ofThe massiveMIMO channel has largenull spaces in whichinformation over frequency just is not possible.MassiveMIMO offers the methods of improving robustness ofnearly everything can be engaged without disturbing theterminals. Precisely modules can be placed into this nullwireless communications with thehelpof multipleantennasspace that makes the transmitted waveforms fulfill theIt provides with an excess of degrees of freedom that canpreferred envelope restraints.Nevertheless, the operativebe useful for canceling the signals from intended jammers.If massive MIMO systems use joint channel estimation andchannels amid the base station and every terminal, can beproceeded without the involvementof PSKtypemodulationdecoding instead of uplink pilots for channel estimationand can take any signal constellation as input [24].then the problem from the intended jammers is considerablyThe considerable improvement in the energy efficiencyreduced [24].The advantages of massive MIMO systems can befacilitatesmassiveMIMOsystemstoworktwostepsoflowerreviewed from an information theoretic point of view.magnitude than with existing technology on the total outputRFpower.This is importantbecausethecellularbase stationsMassive MIMO systems can obtain the promising multi-plexing gain of massive point to point MIMO systems,areconsumingalotofpoweranditisanareaof concern.In addition,ifbasestations that consume lesspower couldbewhile eliminating problems due to unfavorable propagationdrivenbyrenewableresourceslikesolarorwindandthereforeenvironments[29].1214VOLUME 3,2015
A. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging Technologies 2) MASSIVE MIMO SYSTEMS CAN BE PUT TOGETHER WITH THE HELP OF LOW POWER AND LESS COSTLY COMPONENTS Massive MIMO has come up with a change with respect to concept, schemes and execution. Massive MIMO systems use hundreds of less expensive amplifiers in respect to expensive ultra-linear 50 Watt amplifiers because earlier are having an output power in the milliwatt range, which is much better than the latter which are generally being used in conventional systems. It is dissimilar to conventional array schemes, as it will use only a little antenna’s that are being fed from high power amplifiers but having a notable impact. The most significant improvement is about the removal of a large number of expensive and massive items like large coaxial cables [24]. With the use of a large number of antennas in massive MIMO technology the noise, fading and hardware deficits will be averaged because signals from a large number of antennas are combined together in the free space. It condenses the limits on precision and linearity of every single amplifier and radio frequency chain and altogether what matters is their collective action. This will increase the robustness of massive MIMO against fading and failure of one of the antenna elements. A massive MIMO system has degrees of freedom in excess. For example, with 100 antennas, 10 terminals are showing presence while the remaining 90 degrees of freedom are still available. These available degrees of freedom can be exploited by using them for signal shaping which will be hardware friendly. Specifically, each antenna with the use of very cheap and power proficient radio frequency amplifiers can transmit signals having small peak to average ratio [27] and constant envelope [28] at a modest price of increased total radiated power. With the help of constant envelope multiuser precoding, the signals transmitted from each antenna are neither being formed in terms of beam nor by weighing of a symbol. Rather, a wave field is created and sampled with respect to the location of the terminals and they can see precisely the signals what we intended to make them see. Massive MIMO has a vital property which makes it possible. The massive MIMO channel has large null spaces in which nearly everything can be engaged without disturbing the terminals. Precisely modules can be placed into this null space that makes the transmitted waveforms fulfill the preferred envelope restraints. Nevertheless, the operative channels amid the base station and every terminal, can be proceeded without the involvement of PSK type modulation and can take any signal constellation as input [24]. The considerable improvement in the energy efficiency facilitates massive MIMO systems to work two steps of lower magnitude than with existing technology on the total output RF power. This is important because the cellular base stations are consuming a lot of power and it is an area of concern. In addition, if base stations that consume less power could be driven by renewable resources like solar or wind and therefore it is helpful to deploy base stations to the places where electricity is not available. Along with this, the increased concerns of electromagnetic exposure will be considerably less. 3) MASSIVE MIMO PERMITS A SUBSTANTIAL DECREASE IN LATENCY ON THE AIR INTERFACE Latency is the prime area of concern in the next generation networks. In wireless communication, the main cause of latency is fading. This phenomenon occurs amid the base station and terminal, i.e. when the signal is transmitted from the base station, it travels through different multiple paths because of the phenomenon’s like scattering, reflection and diffraction before it reaches the terminal. When the signal through these multiple paths reaches the terminal it will interfere either constructively or destructively, and the case when following waves from these multiple paths interfere destructively, the received signal strength reduces to a considerable low point. If the terminal is caught in a fading dip, then it has to wait for the transmission channel to change until any data can be received. Massive MIMO, due to a large number of antennas and with the idea of beam forming can avoid fading dips and now latency cannot be further decreased [24]. 4) MASSIVE MIMO MAKES THE MULTIPLE ACCESS LAYER SIMPLE With the arrival of Massive MIMO, the channel strengthens and now frequency domain scheduling is not enough. OFDM provides, each subcarrier in a massive MIMO system with considerably the same channel gain due to which each and every terminal can be provided with complete bandwidth, which reduces most of the physical layer control signaling terminated [24]. 5) MASSIVE MIMO INCREASES THE STRENGTH EQUALLY AGAINST UNINTENDED MAN MADE INTERFERENCE AND INTENDED JAMMING Jamming of the wireless systems of the civilian is a prime area of concern and poses a serious threat to cyber security. Owing to limited bandwidth, the distribution of information over frequency just is not possible. Massive MIMO offers the methods of improving robustness of wireless communications with the help of multiple antennas. It provides with an excess of degrees of freedom that can be useful for canceling the signals from intended jammers. If massive MIMO systems use joint channel estimation and decoding instead of uplink pilots for channel estimation, then the problem from the intended jammers is considerably reduced [24]. The advantages of massive MIMO systems can be reviewed from an information theoretic point of view. Massive MIMO systems can obtain the promising multiplexing gain of massive point to point MIMO systems, while eliminating problems due to unfavorable propagation environments [29]. 1214 VOLUME 3, 2015
IEEEAcceSSA. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging TechnologiesLetusstudyamassiveMIMOsystemhavingLcells,whereAn exhaustivedebateabout thisresult can be seen in[31]every cell has K attended single antenna users and one baseCentered on the result in (6), the overall achievablerate of allstation with N antennas.hi.k,l.n represent the channel coeffi-users cometo becient from the k-th user in the l-th cell to the n-th antenna ofC= log2 det(I + puHHH)the i-th base station, which is equivalent to a complex small~ logz det (I + N pD)scalefading factor time an amplitude factorthat interprets forKbitsgeometric attenuation and large-scale fading:log2 (1 +Npude)(7)Hzk=l(1)hik,In = gi.k,I,nVdik.Capacity in (7)can be achieved at the base station byWhere gi.k.l.n and dik,/represent complex small scalefadsimple MF processing.When MF processing is used, theingand large scalefadingcoefficients,respectively.Thesmallbase station processes the signal vectorby multiplying thescale fading coefficients are implicit to be diverse for diverseconjugate transpose of the channel, asusers or for diverse antennas at every base station thoughHyu= HH (VPHXu + nu)the large scale fading coefficients are the same for diverseantennasatthe samebase station,butareuserdependent.~NpuDxu+HHnu(8)Then, the channel matrix from all K users in the I-th cell towhere (6) is used. Note that the channel vectors are asympthe i-th base station can be expressed astotically orthogonal when the number of antennas at thebasehi.K,I,1station grows to infinity. So, HH does not shade the noise.(hi,1,1.1...= G,ID2Since D is a diagonal matrix,the MF processing splits theHil=..."(2)signals from diverse users into diverse streams and there is(hi,1,I,Nhi,K.I,N.asymptotically no inter user interference.So nowthe signalWheretransmission can betreated as a SISO channel transmissionfor each user.From (8), the signal to noise ratio (SNR) for the...gi,k,,1gi,1,1,1k-th userisNpudk.Subsequently,theattainableratebyusing:...(3)Gi,1 =...MF is similar as the limit in (7), which indicates that simpleMFprocessingatthebasestationisbestwhenthenumberofgi,1,1,ngi.K,I,Nantennas at the base station, N,grows to infinity.( di,1)..+Di.c=++.(4)tt....b:DOWNLINKyad e cK*l can be denoted as the received signal vector at...dik,).all K users. Massive MIMO works properly in time divisionLet us study a single cell (L = 1) massive MIMO systemduplexing (TDD) mode as discussed in [29], where the down-with K singled antenna users and a base station withlink channel is the transpose of the uplink channel matrixN antennas.For ease,the cell and the base station indices areThen, the received signal vector can be expressed asplunged when single cell systems are deliberated [29].yd =paH' xd+ nd(9)Q:UPLINKwhere xd e CN+I is the signal vector transmitted by theThe received signal vector at a single base station for uplinkbase station, nd e CK+l is an additive noise and pd is thesignal transmission is denoted as yu e CN*l,can be stated as:transmit power of the downlink. Let us assume, E[xa] = 1for normalizing transmitting power.(5)yu=PuHxu+nuAs discussed in [29], the base station usually has channelstate information equivalent to all users based on uplink pilotwhere Xu e cK*l is the signal vector from all users,transmission.So, it is likely for thebase station to dopowerH e CN*K is the uplink channel matrix defined in (2) byallocationformaximizing the sumtransmission rate.Thesumreducing the cell and the base station indices, nu e CNl iscapacity of thesystemwithpowerallocation is [32]azeromeannoisevectorwithcomplexGaussiandistributionand identity covariance matrix, and pu is the uplink transmitC = max log, det(IN + PaHPHH)power.The transmitted symbol from the k-th user, x,is thebitsk-th element of xu = [x"..., x] with [x'] =- 1.~maxlog2det(Ik+paNPD)(10)HzThe column channel vectors from diverse users areasymptotically orthogonal as thenumber of antennasatthebasewhere (6) is used and P is a positive diagonal matrix withstation,N,grows to infinity by supposing that the smallthe power allocations (pi,..... pk)as its diagonal elementsscale fading coefficients for diverse users is independent [30]]and Zk=I Pk = 1Then, we haveIf the MF precoder is used, the transmitted signal vector isHHH = D1/2GHGDI/2~NDI/21kD/2= NDXd = H *D-1/2pl/2sd(6)(11)1215VOLUME 3, 2015
A. Gupta, R. K. Jha: Survey of 5G Network: Architecture and Emerging Technologies Let us study a massive MIMO system having L cells, where every cell has K attended single antenna users and one base station with N antennas. hi,k,l,n represent the channel coeffi- cient from the k-th user in the l-th cell to the n-th antenna of the i-th base station, which is equivalent to a complex small scale fading factor time an amplitude factor that interprets for geometric attenuation and large-scale fading: hi,k,l,n = gi,k,l,n p di,k,l (1) Where gi,k,l,n and di,k,l represent complex small scale fading and large scale fading coefficients, respectively. The small scale fading coefficients are implicit to be diverse for diverse users or for diverse antennas at every base station though the large scale fading coefficients are the same for diverse antennas at the same base station, but are user dependent. Then, the channel matrix from all K users in the l-th cell to the i-th base station can be expressed as Hi,l = hi,1,l,1 · · · hi,K,l,1 . . . . . . . . . hi,1,l,N · · · hi,K,l,N = Gi,lD 1/2 i,l (2) Where Gi,l = gi,1,l,1 · · · gi,K,l,1 . . . . . . . . . gi,1,l,N · · · gi.K,l,N (3) Di,c = di,1,l · · · . . . . . . . . . . . . . . . · · · di.K,l (4) Let us study a single cell (L = 1) massive MIMO system with K singled antenna users and a base station with N antennas. For ease, the cell and the base station indices are plunged when single cell systems are deliberated [29]. a: UPLINK The received signal vector at a single base station for uplink signal transmission is denoted as yu ∈ C N∗1 , can be stated as: yu = √ ρuHxu + nu (5) where xu ∈ C K∗1 is the signal vector from all users, H ∈ C N∗K is the uplink channel matrix defined in (2) by reducing the cell and the base station indices, nu ∈ C N∗1 is a zero mean noise vector with complex Gaussian distribution and identity covariance matrix, and ρu is the uplink transmit power. The transmitted symbol from the k-th user, x u k , is the k-th element of xu = [x u 1 , . . . ., x u K ] T with [|x u k | 2 ] = 1. The column channel vectors from diverse users are asymptotically orthogonal as the number of antennas at the base station, N, grows to infinity by supposing that the small scale fading coefficients for diverse users is independent [30]. Then, we have H H H = D 1/2G H GD1/2 ≈ ND1/2 IKD 1/2 = ND (6) An exhaustive debate about this result can be seen in [31]. Centered on the result in (6), the overall achievable rate of all users come to be C = log2 det(I + ρuH H H) ≈ log2 det (I + NρuD) = X K k=1 log2 (1 + Nρudk ) bits s Hz (7) Capacity in (7) can be achieved at the base station by simple MF processing. When MF processing is used, the base station processes the signal vector by multiplying the conjugate transpose of the channel, as H H yu = H H √ ρuHxu + nu ≈ N √ ρuDxu + H H nu (8) where (6) is used. Note that the channel vectors are asymptotically orthogonal when the number of antennas at the base station grows to infinity. So, H H does not shade the noise. Since D is a diagonal matrix, the MF processing splits the signals from diverse users into diverse streams and there is asymptotically no inter user interference. So now the signal transmission can be treated as a SISO channel transmission for each user. From (8), the signal to noise ratio (SNR) for the k-th user is Nρudk . Subsequently, the attainable rate by using MF is similar as the limit in (7), which indicates that simple MF processing at the base station is best when the number of antennas at the base station, N, grows to infinity. b: DOWNLINK yd ∈ C K∗1 can be denoted as the received signal vector at all K users. Massive MIMO works properly in time division duplexing (TDD) mode as discussed in [29], where the downlink channel is the transpose of the uplink channel matrix. Then, the received signal vector can be expressed as yd = √ ρdH T xd + nd (9) where xd ∈ C N∗1 is the signal vector transmitted by the base station, nd ∈ C K∗1 is an additive noise and ρd is the transmit power of the downlink. Let us assume, E[|xd | 2 ] = 1 for normalizing transmitting power. As discussed in [29], the base station usually has channel state information equivalent to all users based on uplink pilot transmission. So, it is likely for the base station to do power allocation for maximizing the sum transmission rate. The sum capacity of the system with power allocation is [32] C = max p log2 det(IN + ρdHPHH ) ≈ max p log2 det(IK + ρdNPD) bits s Hz (10) where (6) is used and P is a positive diagonal matrix with the power allocations (p1, . . . ., pk ) as its diagonal elements and PK k=1 pk = 1 If the MF precoder is used, the transmitted signal vector is xd = H ∗ D −1/2P 1/2 sd (11) VOLUME 3, 2015 1215