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Long Term Evolution Beyond 3G

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OVERVIEW LTE targets Network architecture LTE Physical layer LTE Access tecniques MIMO Channels LTE Advanced

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LTE TARGETs Packet-Domain-Services only (e.g. VoIP) upon LTE, TCP/IP- based layers Higher peak data rate/ user throughput 100 Mbps DL/50 Mbps UL @20MHz bandwidth Reduced delay/latency user-plane latency

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LTE TARGETs

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Network Architecture

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Network Architecture E-UTRAN User Equipment Evolved Node B (eNB) Functionalities: 1) resource management (allocation and HO) 2) admission control 3) application of negotiated UL QoS 4) cell information broadcast 5) ciphering/deciphering of user and control plane data

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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 retransmissions 2) 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 relocation 3) authentication of users : it checks the authorization of the UE to camp on the service providers Public Land Mobile Network (PLMN) 4) control plane function for mobility between LTE and 2G/3G access

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Network Architecture Evolved Packet Core Serving Gateway Functionalities: 1) routing and forwarding user data packets 2) acts as mobility anchor for the user plane during inter-eNB handovers and for mobility between LTE and other 3GPP 3) for idle state UEs, terminates the DL data path and triggers paging when DL data arrives for the UE 4) performs replication of the user traffic in case of lawful interception.

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Network Architecture Evolved Packet Core Packet Data Network Gateway Functionalities: 1) 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 PDNs 2) performs policy enforcement, packet filtering for each user, charging support, lawful Interception and packet screening 3) acst as the anchor for mobility between 3GPP and non-3GPP technologies (WiMAX)

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LTE PHY Layer + Includes methods for contrasting distortion due to multipath: a) OFDM b) MIMO + New access method scheme: a) OFDMA b) SC-FDMA

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Multipath effects ISI induced by multipath time-domain effect of multipath Frequency selectivity frequency-domain effect of multipath

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Spectrum flexibility Possibility 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

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Orthogonal Frequency Division Multiplexing Eliminates ISI problems simplification of channel equalization OFDM 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!!!

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Orthogonal Frequency Division Multiplexing Cyclic prefix duration linked with highest degree of delay spread Possible interference within a CP of two symbols FTT PERIOD

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OFDM Problems Zero 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

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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:

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Orthogonal Frequency Division Multiple Access Resource element 1 subcarrier for each symbol period PRB is the smallest element for resource allocation contains 12 consecutives subcarriers for 1 slot duration

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Orthogonal Frequency Division Multiple Access CARRIER ESTIMATION PHY preamble not used for carrier set Use of reference signals transmitted in specific position (e.g. I and V OFDM symbols) every 6 sub-carriers INTERPOLATION is used for estimation of other sub-carriers

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Multiple Input Multiple Output MIMO CHANNEL Definition of a time-varying channel response for each antenna:

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Multiple Input Multiple Output In LTE each channel response is estimated thanks to pilot signals transmitted for each antenna When an antenna is transmitting her references, the others are idle. Once the channel matrix is known, data are transmitted simultaneously.

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Multiple Input Multiple Output Advantages: 1) Higher data rate more than one flow simultaneously 2) Spatial diversity taking advantage from multiple paths multipath as a resource - Disadvantages: 1) Complexity LTE admitted configurations: - UL: 1x1,1x2 -DL: 1x1, 1x2, 2x2, 4x2

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Multiple Input Multiple Output MIMO techniques in LTE: 1) SU-MIMO 2) Transmit diversity 3) Closed loop rank 1 4) MU- MIMO 5) Beamforming

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Single User MIMO Two way to work: - Closed Loop - Open Loop CLOSED LOOP SU-MIMO eNodeB applies a pre-codification on the transmitted signal, according to the UE channel perception. Tx Rx -RI: rank indicator -PMI: Precoding Matrix Indicator -CQI: Channel Quality Indicator

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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. Tx Rx

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Other MIMO Techniques Transmit 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.

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Single Carrier FDMA Access 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.

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Single Carrier FDMA

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2 ways for mapping sub-carriers Assigning group of frequencies with good propagation conditions for UL UE The subcarrier bandwidth is related to the Doppler effect when the mobile velocity is about 250 Km/h

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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 information - Only available modulation (QPSK) robustness preferred

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DL CHANNELS and SIGNALS Common Control Physical Channel (CCPCH) - Cell wide control information - Only QPSK available - Transmitted as closed as the center frequency as possible Physical signals: convey information used only in PHY layer 1) Reference signals for channel response estimation (CIR) 2) Synchronization signals for network timing

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TRANSPORT CHANNELS 1) Broadcast channel (BCH) 2) Downlink Shared channel (DL-SCH) - Link adaptation - Suitable for using beamforming - Discontinuous receiving/ power saving 1) Paging channel (PGH) 2) Multicast channel (MCH)

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UL CHANNELS Physical Uplink Shared Channel (PUSCH) - BPSK, 16 QAM, 64 QAM Physical Uplink Control Channel (PUCCH) - Convey channel quality information - ACK - Scheduling request Uplink Shared channel (UL-SCH) Random Access Channel (RACH)

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UL SIGNALS Random Access Preamble transmitted by UE when cell searching starts Reference signal

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CHANNEL MAPPING DOWNLINK UPLINK

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Beyond the future: LTE Advanced Relay NodesUERelay NodesUE Dual TX antenna solutions for SU-MIMO and diversity MIMO Dual TX antenna solutions for SU-MIMO and diversity MIMO Scalable system bandwidth exceeding 20 MHz, Potentially up to 100 MHz Scalable system bandwidth exceeding 20 MHz, Potentially up to 100 MHz Local area optimization of air interfaceNomadic / Local Area network and mobility solutions Local area optimization of air interfaceNomadic / Local Area network and mobility solutions Flexible Spectrum Usage / Cognitive radio Flexible Spectrum UsageCognitive radio Automatic and autonomous network configuration and operation Automatic and autonomous network configuration and operation Enhanced precoding and forward error correction Enhanced precoding and forward error correction Interference management and suppression Interference management and suppression Asymmetric bandwidth assignment for FDD Asymmetric bandwidth assignment for FDD Hybrid OFDMA and SC-FDMA in uplinkUL/DL inter eNB coordinated MIMO Hybrid OFDMA and SC-FDMA in uplinkUL/DL inter eNB coordinated MIMO