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