What is LTE and what are the advantages of LTE?

1. Simnovus Tech Private Limited 520-523, City Centre,PlotNo.05, Sector-12, Dwarka, NewDelhi-110075

2. SIMNOVUS.COM INTRODUCTION TOLTE The Third Generation ( 3 G/HSPA) of wireless mobile telecommunication technology led to tremendous growth in usage of mobile data. Mobile internet access extended from laptop usage to smart phones, thus facilitating development in mobile network performance towards very high instant peak data rates and very low latencies. Huge growth in mobile users and their traffic to be carried by mobile networks demands significant increase in system capacity that, inturn, instigates a new technological solution to network design. When high capacity and high performance at f lat pricing are offered to the end customer, then cost per bit becomes a critical issue for the service provider. These have led to the specification of a Long Term Evolution ( LTE) of UTRAN while a mobile system core specification is defined as a System Architecture Evolution ( SAE), also called Evolved Packet Core ( EPC). LTE together with EPC forms the Evolved Packet System( EPS). In order to satisfy capacity demands, an additional portion of radio spectrum was released for LTE in the 2 . 6 GHz to 700 MHz range. New radio technology deployed in LTE delivers high spectrum efficiency and high capacity. A major reduction incost per bit is ensured with f lat IP-based LTE network architecture, cost efficient high bandwidth backhaul and transportnetwork. The 3 GPP has set performance targets for an LTE of peak data rates > 100 Mbps in DL and > 50 Mbps in UL with latency less than 5 ms on the air interface per l ink. The access scheme in LTE is OFDMA in downlink and a SC-FDMA in uplink. OFDM allowsforimproved interference control, advanced scheduling techniques and ease of implementation of MIMOto improve spectrum efficiency.

3. SIMNOVUS.COM FEATURESOF LTE LTE has introduced a number of new technologies. They enable LTE tobe able to operate more efficiently with respect to the use of spectrum, and also provide the much higher data rates that are beingrequired. OFDMA ( Orthogonal Frequency Division Multiple Access): Using OFDMAin the downlink. This technology allows multiple access by dividing channels into a set of orthogonal subcarriers that are distributed into groups depending on the needs of eachuser. SC-FDMA ( Single Carrier Frequency Division Multiple Access): Usingof SC-FDMA in the uplink. The disadvantage of OFDMA is the existence of significant variations of power in output signals. Since power consumption is very important for the uplink, SC-FDMA isused. MIMO ( Multiple Input Multiple Output): One of the main problemsthat previous telecommunications systems have encountered was that of multiple signals arising from the many reflections that are encountered. By using MIMO, these additional signal paths could be used to advantage and were able to be used to increase thethroughput.

4. SIMNOVUS.COM FEATURESOF LTE SAE ( System Architecture Evolution): System Architecture Evolution is a new network architecture to simplify LTE networks. SAE uses eNodeB and Access Gateway and removes RNC and SGGN from 3 G network architecture to simplify the mobilenetwork. FDD and TDD: LTE uses both Time Division Duplex ( TDD) and Frequency Division Duplex ( FDD) mode. In FDD uplink and downlink transmission use different frequencies, while in TDD both uplink and downlink use the same carrier and are separated inTime. Spectrum Flexibility: LTE supports f lexible carrier bandwidths, from 1 . 4 MHz up to 20 MHz as well as both FDD and TDD. LTE designed with a scalable carrier bandwidth from 1 . 4 MHz up to 20 MHz which bandwidth is used depends on the frequency band and the amount of spectrum available with a networkoperator. Qo S ( Quality of Service): Qo S mechanisms have been standardized on all interfaces to ensure that the requirement of voice calls for a constant delay and bandwidth, can still be met when capacity l imits arereached. ICIC( Inter-Cell Interference Coordination): LTE allowscoordination between different base stations in order to identify which users are located in the center or the edge of the cell. The use of different frequency reuse schemes can reduce inter-cellularinterference.

5. SIMNOVUS.COM ADVANTAGESOF LTE Simplifiedarchitecture. High data rates can be achieved in both downlink as well as uplink. This causes highthroughput. Flexiblebandwidths. Time required to connect to the network is in the range of a few hundred milliseconds and power saving states can now be entered and exited very quickly. Frequency Division Duplex ( FDD) and Time Division Duplex ( TDD), both schemes can be used on the sameplatform. Optimized signaling for connection establishment and other airinterface and mobility management procedures have further improved the user experience. Latency reduced ( to 10ms) for better userexperience. LTE will also support seamless connection to existing networks such as GSM, CDMA andWCDMA. More number of users can send or receive data simultaneously. Higher order MIMO can beused. High spectrum efficiency. No power limitation. More number of symbols can be used in one carrier. We use shared channels not only dedicatedchannels. The user does not have to manually install drivers for the device. Instead the system automatically recognizes the device, loads new drivers for the hardware i f needed, and begins to work with the newly connecteddevice.

6. SIMNOVUS.COM LTERELEASES

7. SIMNOVUS.COM LTE NETWORK ARCHITECTURE Thehigh-levelarchitectureoftheEvolvedPacketSystem(EPS)consistsmainlyofthreecomponents, namely the User Equipment (UE), the Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) and the Evolved Packet Core (EPC). In turn, the Evolved Packet Core communicates with packet data networksintheoutsideworldsuchastheinternet,privatecorporatenetworksortheIPmultimedia subsystem.TheinterfacesbetweenthedifferentpartsofthesystemaredenotedUu,S1andSGi. Fig. Evolved Packet System(EPS)

8. SIMNOVUS.COM USER EQUIPMENT(UE) TheUE,EUTRANandEPCeachhavetheirowninternalarchitectureandwewillnow discuss these one byone. The internal architecture of the user equipment of LTE is identical to the one used by UMTS and GSM which is actually a Mobile Equipment (ME). The mobile equipment comprised of the following importantmodules: Mobile Termination (MT): This handles all the communication functions. Terminal Equipment (TE): This terminates the datastreams. Universal Integrated Circuit Card (UICC): This is also known as the SIM card for LTE equipment. It runs an application known as theUniversal Subscriber Identity Module (USIM). EVOLVEDUMTSTERRESTRIALRADIOACCESS NETWORK(E-UTRAN) The evolved UMTS terrestrial radio access network (E-UTRAN). The E-UTRAN handles the radio communications between the mobile and the evolved packet core and has just one component, the evolved Node B (eNB oreNodeB). Each eNodeB is a base station that controls the mobiles in one or more cells.A mobile communicates with just one base station and one cell at a time, so there is no equivalent of the soft handover state from UMTS. The base station that is communicating with a mobile is known as its servingeNodeB.

9. SIMNOVUS.COM The eNodeB has two main functions. Firstly, transmissions to all its mobiles on the transmissions from them on the uplink, using the eNodeB sends radio downlink and receives the analogue and digital signalprocessingfunctionsoftheLTEairinterface.Secondly,theeNodeB controlsthelow-leveloperationofallitsmobiles,bysendingthem signalingmessagessuchashandovercommandsthatrelatetothoseradio transmissions. TheeNodeBcombinestheearlierfunctionsoftheNodeBandtheradio networkcontroller,toreducethelatencythatariseswhenthemobile exchangesinformationwiththenetwork. EachbasestationisconnectedtotheEPCbymeansoftheS1interface.It canalsobeconnected tonearbybasestationsbytheX2interface,which ismainlyusedforsignaling andpacketforwardingduring handover.

10. SIMNOVUS.COM EVOLVEDPACKET CORE(EPC) TheEvolvedPacketCore(EPC)istheLTEcorenetwork.Itconsistsof componentsthathavethefollowingfunctionalities:mobilitymanagement, authentication,qualityof service,routinguploadanddownloadIP packets,IPaddressallocation,andmore. TheEPChasaflatIParchitecturethatallowsthenetworktohandlea greatamountof datatrafficinanefficientandcost-effectivemanner. TheLTEEPCarchitectureconsistsofMME,SGW,PGW,HSSandPCRF. Wewill nowdiscusstheseonebyone.

11. SIMNOVUS.COM MOBILITY MANAGEMENT ENTITY(MME) MobilityManagementEntity(MME),whichisthecontrolplane(C-plane) functionalelementinEPC.MMEmanagesandstoresUEcontext,generates temporaryidentitiesandallocatesthemtoUEs,authenticatestheuser, managesmobilityandbearersandactsasaterminationpointforNon- AccessStratum(NAS)signaling. TheMMEhasfollowingfunctionalities: Authentication :enablesUEstoauthenticatetothenetworkbyexchanging authenticationinformationbetweentheUEandtheHSS. Mobilitymanagement :allows thesubscriber’smobilitywithinthenetwork oracrossnetworks. Locationupdate:keepstrackofthesubscriber’slocationwithinthe network,andofitscurrentstate. Bearerestablishment :establishesbearersbydeciding onagatewayrouter totheInternetiftherearemoregatewaysavailable. Handoversupport :enableshandoverbetweeneNodeB’s(forhandoveron theS1interface). TheMMEalso controlplane networkswith TheMMEalso roamingUEs. supportslawfulinterceptionofsignaling.Itprovidesthe functionformobility betweenLTEand2G/3Gaccess theS3interfaceterminatingattheMMEfromtheSGSN. terminatestheS6ainterfacetowardsthehomeHSSfor

12. SIMNOVUS.COM SERVINGGATEWAY (S-GW) Theservinggateway(S-GW)actsasahigh-levelrouter,andforwardsdata betweenthebasestationandthePDNgateway.Atypicalnetworkmight containahandfulofservinggateways,eachofwhichlooksafterthe mobilesinacertaingeographicalregion.Eachmobileisassignedtoa singleservinggateway,buttheservinggatewaycanbechangedifthe mobilemovessufficientlyfar. ServesEPC(U-Plane),E-UTRAN(S1-U). S-GWactsasalocalmobilityentityforintereNodeBhandovers. S-GWactsasamobility anchorfor3GPPmobility. S -GW responsible for packet routing and forwarding, buffering downlinkpackets. S -GW performs replication of the user traffic in case of lawful interception.

13. SIMNOVUS.COM PDNGATEWAY (PDN-GW) Thepacketdatanetworkgateway(P-GW)istheEPC’spointofcontact withtheoutsideworldthroughtheSGiinterface,eachPDNgateway exchangesdatawithoneormoreexternaldevicesorpacketdata networks,suchasthenetworkoperator’sservers,theinternetortheIP multimediasubsystem.Eachpacketdatanetworkisidentifiedbyanaccess pointname(APN).Anetworkoperatortypicallyusesahandfulofdifferent APNs;forexample,onefortheinternetandonefortheIPmultimedia subsystem. EachmobileisassignedtoadefaultPDNgatewaywhenitfirstswitches on,togiveitalways-onconnectivitytoadefaultpacketdatanetwork suchastheinternet.Lateron,amobilemaybeassignedtooneormore additionalPDNgateways,ifitwishestoconnecttoadditionalpacketdata networkssuchasprivatecorporatenetworksortheIPmultimedia subsystem.EachPDNgatewaystaysthesamethroughoutthelifetimeof thedataconnection. ServesSGiinterfacetowardsPDN. UEIP addressallocation. Mobility anchorforinternetworkingwithnon-3GPPnetworks. DLpacketfilteringandassignmenttoEPSbearers(QoS)basedonTFTs. QoS enforcementandflowbased-chargingaccordingtorulesfromPCRF (Policy andChargingEnforcementFunction–PCEF)

14. SIMNOVUS.COM HOMESUBSCRIBER SERVER(HSS) TheHSSisacentraldatabasethatcontainsuser-relatedandsubscription- relatedinformation.ThefunctionsoftheHSSincludefunctionalitiessuch asmobilitymanagement,callandsessionestablishmentsupport,user authenticationandaccessauthentication.Italsoholdsinformationabout thePDNstowhichtheusercanconnect.InadditiontheHSSholds dynamicinformationsuchastheidentityoftheMMEtowhichtheuseris currentlyattachedorregistered.TheHSSmayalsointegratethe authenticationcenter(AUC),whichgeneratesthevectorsfor authenticationandsecuritykeys. PolicyControlandChargingRulesFunction(PCRF) ThePCRFisresponsiblefor policycontroldecisionmakingaswellasfor controllingtheflow-basedchargingfunctionalitiesinthepolicycontrol enforcementfunction(PCEF),whichresidesintheP-GW.ThePCRF providestheQoSauthenticationthatdecideshowacertaindataflowwill betreatedinthePCEFandensuresthatthisisinaccordancewiththe user’ssubscriptionprofile.

15. SIMNOVUS.COM AIR INTERFACE PROTOCOLSTACK TheAirInterfaceProtocolStackcanbedividedintotwopartsoneisa userplaneandanotheracontrolplane.Theuserplanemainlyusedfor actualdataflowwhilethecontrolplaneusedfortheconfigureuserplane layersbeforeactualdataflow. Intheuserplane,theapplicationcreatesdatapacketsthatareprocessed byprotocolssuchasTCP,UDPandIP,whileinthecontrolplane;the radioresourcecontrol(RRC)protocolwritesthesignalingmessagesthat areexchangedbetweenthebasestationandthemobile.Inbothcases,the informationisprocessedbythepacketdataconvergenceprotocol(PDCP), theradiolinkcontrol(RLC)protocolandthemediumaccesscontrol(MAC) protocol,beforebeing passedtothephysicallayerfortransmission.

16. SIMNOVUS.COM USERPLANE TheUserplaneprotocolstackconsistsoflayersPDCP,RLC,MAC. Nowdiscussfunctionalityofeachlayeronebyone. PacketDataConvergenceProtocol(PDCP) T he P D C P protocol l ay er i s part of L T E ai r i nterf ace control and user planes. ThefunctionalitiesofthePDCPsublayerfortheuserplaneinclude: T he P D C P l ay er i s responsi bl e f or compressi on and decompression of the headers of user pl ane I P pack ets usi ngrobust enableefficientuseofairinterfacebandwidth. T ransf er of userdata. In-sequencedeliveryofupperlayerPDUsat procedure f or R L C A M. Duplicate detection of lower layer SDUs at header compressi onto PDCP re-establishment PDCP re-establishment procedure f or R L C A M. RetransmissionofPDCPSDUsathandoverforRLCAM. Cipheringanddeciphering. S ecuri ty ofdata. Timer-basedSDUdiscardinuplink.

17. SIMNOVUS.COM RADIO LINK CONTROL(RLC) The RLC protocol layer exists in UE &eNodeB; it is part of LTE air interfacecontrol and user planes. The main services and functions ofthe RLC sub layer include: The RLC layer used to format, transport traffic between the UE and the eNodeB. RLC provides three different reliability modes for datatransport Acknowledged Mode (AM) Unacknowledged Mode (UM) Transport Mode (TM) UM mode is suitable for transport of real time services because such services are delay sensitive and cannot wait forretransmissions. AM mode is appropriate for non-RT ( NRT) services such as filedownloads. TM mode is used when the PDU sizes are known a priori such as for broadcasting systeminformation. RLC layer also provides in sequence delivery of service data units ( SDU’ s) to the upper layers and eliminates duplicate SDUs from being delivered to the upper layers. RLC offers services to PDCP in the form of radio bearers. These radio bearers are mapped to EPS bearers in EPC. Concatenation, segmentation and reassembly of RLC SDUs ( only for UM and AM datatransfer). Re-segmentation of RLC data PDUs ( only for AM data transfer). Recording of RLC data PDUs ( only for UM and AM data transfer). Duplicate detection ( only for UM and AM datatransfer). Protocol error detection ( only for AM datatransfer).

18. SIMNOVUS.COM MEDIUMACCESS CONTROL(MAC) TheMACprotocollayerexistsinUE&eNodeB; itispartofLTEair interface controlanduserplanes.The mainservicesandfunctionsofthe MACsublayerinclude: Mappingbetweenlogicalchannelsandtransportchannels. Multiplexing/demultiplexingofMACSDUsbelongingtooneordifferent logicalchannelsinto/fromtransportblocks(TB)deliveredto/fromthe physicallayerontransportchannels. Scheduleinformationreporting. Errorcorrectionthroughhybridautomaticrepeatrequest(HARQ). PriorityhandlingbetweenlogicalchannelsofoneUE. Priorityhandling betweenUEsbymeansofdynamicscheduling. Logicalchannelprioritization. Transportformatselection.

19. SIMNOVUS.COM CONTROLPLANE The controlplane protocolstackconsistsoflayersNAS,RRC,PDCP,RLC, andMAC.Nowdiscusseachlayerfunctionalityonebyone. NonAccessStratum(NAS) TheNonAccessStratum(NAS)is thehigheststratumofthecontrolplane betweenUE andMME attheradiointerface.Mainfunctionsofthe protocolsthatarepartoftheNASare thesupportofmobilityoftheuserequipment(UE)andthesupportof sessionmanagementprocedurestoestablish and maintainIPconnectivity betweentheUEandapacketdatanetworkgateway(PDNGW).NAScontrol protocolperforms followings: EPSbearermanagement. Authentication. ECM-IDLEmobilityhandling. PagingoriginationinECM-IDLE. NASSecuritycontrol.

20. SIMNOVUS.COM RADIORESOURCE CONTROL(RRC) TheRRCprotocollayer interfacecontrolplane. layerinclude: exists in UE & eNodeB; it is part of the LTE air The main services and functions of the RRC sub BroadcastofSystemInformationrelatedtothenon-accessstratum (NAS). BroadcastofSystemInformationrelatedtotheaccessstratum(AS). Paging. Establishment,maintenanceandreleaseofanRRCconnection between theUEandE-UTRAN. Securityfunctionsincludingkeymanagement. Establishment,configuration,maintenanceandreleaseofpointtopoint radioBearers. Mobilityfunctions. QoSmanagementfunctions. UEmeasurementreportingandcontrolofthereporting. NASdirectmessagetransferto/fromNASfrom/toUE. PDCP, R LC, MAC layer functionalities of control plane al so same as mentionedinuserplane.

21. SIMNOVUS.COM PHYSICALLAYER TheLTEairinterfacephysicallayeroffersdatatransportservicesto higherlayers.Theaccesstotheseservicesisthroughtheuseofa transportchannelviatheMACsublayer. Thephysicallayerisexpectedtoperformthefollowingfunctionsin ordertoprovidethedatatransportservice: FECencoding/decodingofthetransportchannel. HybridARQsoft-combining. Transportblockerrorindicationtohigherlayers. Ratematching ofthecodedtransportchanneltophysicalchannels. Mappingofthecodedtransportchannelontophysicalchannels. Powerweightingofphysicalchannels. Modulationanddemodulationofphysicalchannels. Frequency andtimesynchronization. Radiocharacteristicsmeasurementsandindicationtohigherlayers. MultipleInputMultipleOutput(MIMO)antennaprocessing. TransmitDiversity(TXdiversity). RFprocessing. References : https://www.tutorialspoint.com/lte/lte_overview.htm https://www.learnwirelesstechnology.com/lte-protocol-stack/ https://yatebts.com/documentation/concepts/lte- concepts/#The_EPC

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