Long Term Evolution/LTE
Access Network for EPC/SAE NetworksINAM ULLAHHead of Product DevelopmentTURNOTECH
Why LTE/SAE?LTE OverviewLTE technical objectives SAE architechtureLTE Radio interfaceLTE RAN InterfacesFunctions of eNBContentsPacket Switched data is becoming more and more dominantVoIP is the most efficient method to transfer voice data Need for PS optimised systemAmount of data is continuously growingNeed for higher data rates at lower costUsers demand better quality to accept new servicesHigh quality needs to be quaranteed Alternative solution for non-3GPP technologies (WiMAX) neededLTE will enhance the system to satisfy these requirements.Why LTE3GPP Long Term Evolution/LTE, wireless communication standard by 3GPP for high-speed data for mobile phones and data terminals. LTE is the Radio Access Network for Evolved Packet Core (EPC/EPS/SAE) Its an Evolution fromGSM/GPRS/EDGEand UMTS/HSPAnetwork technologies, for increasing the capacity and speed using newmodulation/DSP(Digital Signal Processing) techniques Its wireless interface is incompatible with2Gand3Gnetworks, and so it must be operated on a separatewireless spectrum ( not Handovers) LTE OverviewUser throughput [/MHz]:Downlink: 3 to 4 times Release 6 HSDPA Uplink: 2 to 3 times Release 6 Enhanced Uplink Downlink Capacity: Peak data rate of 100 Mbps in 20 MHz maximum bandwidthUplink capacity: Peak data rate of 50 Mbps in 20 MHz maximum bandwidthLatency: Transition time less than 5 ms in ideal conditions (user plane), 100 ms control plane (fast connection setup)Mobility: Optimised for low speed but supporting 120 km/hMost data users are less mobile!Simplified architecture: Simpler E-UTRAN architecture: no RNC, no CS domain, Scalable bandwidth: 1.25MHz to 20MHz: Deployment possible in GSM bands.
LTE ObjectivesSAE Architecture
Evolved Radio Access Network (eRAN)Consists of the eNodeB (eNB) Offers Radio Resource Control (RRC) functionality Radio Resource Management, admission control, scheduling, ciphering/deciphering of user and control plane data, and compression/decompression in DL/UL user plane packet headersServing Gateway (SGW)Routes and forwards user data packetsActs as the mobility anchor for the user planeDuring inter-eNB handoversBetween LTE and other 3GPP technologiesPages idle state UE when DL data arrives for the UEPacket Data Network Gateway (PDN GW)Provides connectivity to the UE to external packet data networksA UE may have simultaneous connectivity with more than one PDN GWPerforms policy enforcement, packet filtering, and charge supportActs as mobility anchor between 3GPP and no-3GPP technologiesMobility Management Entity (MME)Manages and stores UE contextsUE/user identities, UE mobility state, user security parametersPaging message distribution
SAE/EPS Network ComponentsLTE Architecture
LTE vs UMTS
OFDM (Orthogonal Frequency Division Multiplex):OFDM technology has been incorporated into LTE because it enables high data bandwidths to be transmitted efficiently while still providing a high degree of resilience to reflections and interference.
SC-FDMA (Single Carrier - Frequency Division Multiple Access) is used in the uplink. SC-FDMA is used in view of the fact that its peak to average power ratio is small and the more constant power enables high RF power amplifier efficiency in the mobile handsets - an important factor for battery power equipment.
MIMO (Multiple Input Multiple Output):One of the main problems that previous telecommunications systems has encountered is that of multiple signals arising from the many reflections that are encountered. By using MIMO, these additional signal paths can be used to advantage and are able to be used to increase the throughput.
LTE radio interface
Terminates RRC, RLC and MAC protocols and takes care of Radio Resource Management functionsControls radio bearersControls radio admissionsControls mobility connectionsAllocates radio resources dynamically (scheduling)Receives measurement reports from UESelects MME at UE attachmentSchedules and transmits paging messages coming from MMESchedules and transmits broadcast information coming from MME & O&MDecides measurement report configuration for mobility and schedulingDoes IP header compression and encryption of user data streamsFunctions of eNBLTE RAN InterfacesInterfaces using IP over E1/T1/ATM/Ethernet /X2 interface between eNBs for handoversHandover in 10 msNo soft handovers S1 Interface for Load sharing S1 divided to S1-U (to UPE) and S1-C (to CPE) Single node failure has limited effects
LTE RAN InterfacesProvides non guaranteed delivery of user plane PDUs between the eNB and the SGW. The transport network layer is built on IP transport and GTP-U is used on top of UDP/IP to carry the user plane PDUs between the eNB and the S-GW.S1- Interface (User Interface)The SCTP layer provides the guaranteed delivery of application layer messages.The transport network layer is built on IP transport, similarly to the user plane but for the reliable transport of signaling messages SCTP is added on top of IP. The application layer signaling protocol is referred to as S1-AP (S1 Application Protocol).S1 interface ( control plane )The X2 control plane interface (X2-CP)The application layer signaling protocol is referred to as X2-AP (X2 Application Protocol).The transport network layer of X-2 is built on SCTP on top of IP. FunctionsIntra LTE-Access-System Mobility Support for UE in EMM-CONNECTED:Context transfer from source eNB to target eNB;Control of user plane tunnels between source eNB and target eNB;Handover cancellation.Uplink Load ManagementGeneral X2 management and error handling functions:Error indication.X2 InterfaceLTE Distributed Intelligence The eNBs are connected directly to the core network gateway via a newly defined "S1 interface". In addition to this the new eNBs also connect to adjacent eNBs in a mesh via an "X2 interface". This provides a much greater level of direct interconnectivity. It also enables many calls to be routed very directly as a large number of calls and connections are to other mobiles in the same or adjacent cells. The new structure allows many calls to be routed far more directly and with only minimum interaction with the core network.In addition to the new Layer 1 and Layer 2 functionality, eNBs handle several other functions. This includes the radio resource control including admission control, load balancing and radio mobility control including handover decisions for the mobile or user equipment (UE).The additional levels of flexibility and functionality given to the new eNBs mean that they are more complex than the UMTS and previous generations of base-station. However the new 3G LTE SAE network structure enables far higher levels of performance. In addition to this their flexibility enables them to be updated to handle new upgrades to the system including the transition from 4G LTE to 4G LTE Advanced.
Continued..The new System Architecture Evolution, SAE for LTE provides a new approach for the core network, enabling far higher levels of data to be transported to enable it to support the much higher data rates that will be possible with LTE. In addition to this, other features that enable the CAPEX and OPEX to be reduced when compared to existing systems, thereby enabling higher levels of efficiency to be achieved.Continued..LTE ChannelsPhysical channels: convey info from higher layersPhysical Downlink Shared Channel (PDSCH) - data and multimedia transport - very high data rates supported - BPSK, 16 QAM, 64 QAM Physical Downlink Control Channel (PDCCH) Specific UE informationOnly available modulation (QPSK) robustness preferredCommon Control Physical Channel (CCPCH) Cell wide control informationOnly QPSK availableTransmitted as closed as the center frequency as possible
DL CHANNELS and SIGNALSBroadcast channel (BCH)Downlink Shared channel (DL-SCH) - Link adaptation - Suitable for using beam forming - Discontinuous receiving/ power saving Paging channel (PGH)Multicast channel (MCH)
TRANSPORT CHANNELSPhysical Uplink Shared Channel (PUSCH) BPSK, 16 QAM, 64 QAMPhysical Uplink Control Channel (PUCCH) Convey channel quality informationACKScheduling requestUplink Shared channel (UL-SCH) Random Access Channel (RACH)UL CHANNELSSupport for relay node base stationsCoordinated multipoint (CoMP) transmission and receptionUE Dual TX antenna solutions forSU-MIMOand diversityMIMOScalable systembandwidthexceeding 20MHz, Up to 100MHzCarrier aggregation of contiguous and non-contiguous spectrum allocationsLocal area optimization ofair interfaceNomadic / Local Area network and mobility solutionsFlexiblespectrum usageCognitive radioAutomatic and autonomous network configuration and operationSupport of autonomous network and device test, measurement tied to network management and optimizationEnhancedprecodingandforward error correctionInterference management and suppressionAsymmetric bandwidth assignment forFDDHybridOFDMAandSC-FDMAin uplinkUL/DL intereNBcoordinated MIMOSONs, Self Organized Networks methodologiesMultiple carrier spectrum access.LTE Advanced