3 LTE TARGETsPacket-Domain-Services only (e.g. VoIP) upon LTE, TCP/IP- based layersHigher peak data rate/ user throughput 100 Mbps DL/50 Mbps bandwidthReduced delay/latency user-plane latency<5msImproved spectrum efficiency up to 200 active users in a bandwidthMobility optimized for low-mobility (up to 15Km/h), supported with high performance for medium mobility (up to 120 Km/h), supported for high mobility (up to 500 Km/h)Multimedia broadcast & multicast servicesSpectrum flexibilityMulti-antennas configurationCoverage up to 30 Km
6 Network Architecture – E-UTRAN User EquipmentEvolved Node B (eNB) Functionalities:resource management (allocation and HO)admission controlapplication of negotiated UL QoScell information broadcastciphering/deciphering of user and control plane data
7 Network Architecture Evolved Packet Core Mobility Management Entity key control-node for the LTE ac- cess-network.Functionalities:1) idle mode UE tracking and paging procedure including retransmissions2) bearer activation/deactivation process and choice of the SGW for a UE at the initial attach and at time of intra-LTE handover involving Core Network (CN) node relocation3) authentication of users : it checks the authorization of the UE to camp on the service provider’s Public Land Mobile Network (PLMN)4) control plane function for mobility between LTE and 2G/3G access
8 Network Architecture Evolved Packet Core Serving Gateway Functionalities:routing and forwarding user data packetsacts as mobility anchor for the user plane during inter-eNB handovers and for mobility between LTE and other 3GPPfor idle state UEs, terminates the DL data path and triggers paging when DL data arrives for the UEperforms replication of the user traffic in case of lawful interception.
9 Network Architecture Evolved Packet Core Packet Data Network Gateway Functionalities:provides connectivity to the UE to external packet data networks (IP adresses..). A UE may have simultaneous connectivity with more than one PDN GW for accessing multiple PDNsperforms policy enforcement, packet filtering for each user, charging support, lawful Interception and packet screeningacst as the anchor for mobility between 3GPP and non-3GPP technologies (WiMAX)
10 LTE PHY Layer+ Includes methods for contrasting distortion due to multipath:OFDMMIMO+ New access method scheme:OFDMASC-FDMA
11 Multipath effectsISI induced by multipath time-domain effect of multipathFrequency selectivity frequency-domain effect of multipath
12 Spectrum flexibilityPossibility for using all cellular bands (45o MHz, 800 MHz, 900 MHz, 1700 MHz, 1900 MHz, 2100MHz, 2600MHz)Differently-sized spectrum allocations - up to 20 MHz for high data rates- less than 5 MHz for migration from 2G technologies
13 Orthogonal Frequency Division Multiplexing Eliminates ISI problems simplification of channel equalizationOFDM breaks the bandwidth into multiple narrower QAM-modulated subcarriers (parallel data transmissions) OFDM symbol is a linear combination of signals (each sub-carrier) VERY LONG SYMBOLS!!!
14 Orthogonal Frequency Division Multiplexing Cyclic prefix duration linked with highest degree of delay spreadFTT PERIODPossible interference within a CP of two symbols
15 OFDM ProblemsZero ICI achieved if OFDM symbol is sampled exactly at its center f (14/45 KHz..) FFT is realized at baseband after down-conversion from RF
16 Orthogonal Frequency Division Multiple Access Multiplexing scheme for LTE DL more efficient in terms of LATENCY than classical packet oriented schemes (CSMA/CA)Certain number of sub-carriers assigned to each user for a specific time interval Physical Resource Block (time-frequency dimension)FRAME STRUCTURE:LTE FRAME DURATION 10ms diviso per 10 sub-frameOgni sub-frame è spezzato in 2 time slotOgni slot contiene 6/7 OFMD symbol a seconda del CP
17 Orthogonal Frequency Division Multiple Access PRB is the smallest element for resource allocation contains 12 consecutives subcarriers for 1 slot durationResource element 1 subcarrier for each symbol period
18 Orthogonal Frequency Division Multiple Access CARRIER ESTIMATIONPHY preamble not used for carrier setUse of reference signals transmitted in specific position (e.g. I and V OFDM symbols) every 6 sub-carriersINTERPOLATION is used for estimation of other sub-carriers
19 Multiple Input – Multiple Output MIMO CHANNELDefinition of a time-varying channel response for each antenna:
20 Multiple Input – Multiple Output In LTE each channel response is estimated thanks to pilot signals transmitted for each antennaWhen an antenna is transmitting her references, the others are idle.Once the channel matrix is known, data are transmitted simultaneously.
21 Multiple Input – Multiple Output Advantages:Higher data rate more than one flow simultaneouslySpatial diversity taking advantage from multiple paths multipath as a resourceDisadvantages:ComplexityLTE admitted configurations:- UL: 1x1 ,1x2-DL: 1x1, 1x2, 2x2, 4x2
22 Multiple Input – Multiple Output MIMO techniques in LTE:SU-MIMOTransmit diversityClosed loop rank 1MU- MIMOBeamforming
23 Single User MIMO Two way to work: Closed Loop Open Loop CLOSED LOOP SU-MIMOeNodeB applies a pre-codification on the transmitted signal, according to the UE channel perception.TxRxXY=WXRI, PMI, CQIRI: rank indicatorPMI: Precoding Matrix IndicatorCQI: Channel Quality Indicator
24 Single User MIMO OPEN LOOP SU-MIMO Used when the feedback rate is too low and/or the feedback overhead is too heavy.eNodeB applies a pre-coded cycling scheme to all the transmitted subcarriers .TxRxXY=WX
25 Other MIMO TechniquesTransmit diversity Many different antennas transmit the same signal. At the receiver, the spatial diversity is exploited by using combining techniques. Closed Loop Rank-1 The same as the closed loop with RI=1 this assumption reduces the riTx overhead. Multi User MIMO, MU-MIMO The eNodeB can Tx and Rx from more than one user by using the same time-frequency resource Need of orthogonal reference signals. BEAMFORMING The eNodeB uses the antenna beams as well as an antenna array.
26 Single Carrier FDMAAccess scheme for UL different requirements for power consumption!! OFDMA is affected by a high PAPR (Peak to Average Power Ratio). This fact has a negative influence on the power amplifier development.
28 Single Carrier FDMA 2 ways for mapping sub-carriers Assigning group of frequencies with good propagation conditions for UL UEThe subcarrier bandwidth is related to the Doppler effect when the mobile velocity is about 250 Km/h
29 DL CHANNELS and SIGNALS Physical channels: convey info from higher layers° Physical 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 preferred
30 DL CHANNELS and SIGNALS ° Common Control Physical Channel (CCPCH) Cell wide control informationOnly QPSK availableTransmitted as closed as the center frequency as possiblePhysical signals: convey information used only in PHY layerReference signals for channel response estimation (CIR)Synchronization signals for network timing
31 TRANSPORT CHANNELS Broadcast channel (BCH) Downlink Shared channel (DL-SCH)- Link adaptation- Suitable for using beamforming- Discontinuous receiving/ power savingPaging channel (PGH)Multicast channel (MCH)
35 Beyond the future: LTE Advanced Relay NodesUEDual TX antenna solutions for SU-MIMO and diversity MIMOScalable system bandwidth exceeding 20 MHz, Potentially up to 100 MHzLocal area optimization of air interfaceNomadic / Local Area network and mobility solutionsFlexible Spectrum Usage / Cognitive radioAutomatic and autonomous network configuration and operationEnhanced precoding and forward error correctionInterference management and suppressionAsymmetric bandwidth assignment for FDDHybrid OFDMA and SC-FDMA in uplinkUL/DL inter eNB coordinated MIMO