LTE Introduction Training PPT.ppt

LTE Introduction

3G EvolutionRadio Side (LTE Long Term Evolution)Improvements in spectral efficiency, user throughput, latencySimplification of the radio networkEfficient support of packet based services: MBMS, IMS, etc.Network Side (SAE System Architecture Evolution)Improvement in latency, capacity, throughputSimplification of the core networkOptimization for IP traffic and servicesSimplified support and handover to non-3GPP access technologies

LTE OverviewLTE IntroductionThe access networkPhysical LayerLayer 2 and above over the radio interfaceControl PlaneUser PlaneInterface towards the Core Network

3GPP LTE Architecture

LTE targetsSignificantly increased peak data ratesIncreased cell edge bitratesImproved spectrum efficiencyImproved latencyScaleable bandwidthReduced CAPEX and OPEXAcceptable system and terminal complexity, cost and power consumptionCompatibility with earlier releases and with other systemsOptimised for low mobile speed but supporting high mobile speed

Peak data rateGoal: significantly increased peak data rates, scaled linearly according to spectrum allocationTargets:Instantaneous downlink peak data rate of 100Mbit/s in a 20MHz downlink spectrum (i.e. 5 bit/s/Hz)Instantaneous uplink peak data rate of 50Mbit/s in a 20MHz uplink spectrum (i.e. 2.5 bit/s/Hz)

MobilityThe Enhanced UTRAN (E-UTRAN) will:be optimised for mobile speeds 0 to 15 km/hsupport, with high performance, speeds between 15 and 120 km/hmaintain mobility at speeds between 120 and 350 km/hand even up to 500 km/h depending on frequency bandsupport voice and real-time services over entire speed rangewith quality at least as good as UTRAN

Spectrum issuesSpectrum flexibilityE-UTRA to operate in 1.25, 1.6, 2.5, 5, 10, 15 and 20 MHz allocationshence allowing different possibilities for re-farming already in use spectrumuplink and downlinkpaired and unpairedCo-existencewith GERAN/3G on adjacent channelswith other operators on adjacent channelswith overlapping or adjacent spectrum at country bordersHandover with UTRAN and GERANHandover with non 3GPP Technologies (CDMA 2000, WiFi, WiMAX)

The access networkGeneralityThe access network is simplified and reduce to only the Base Station called eNode BPhysical layer is based on SC FDMA for the Uplink and OFDMA for the DownlinkTwo modes FDD and TDD consideredMBMS part of the studyCiphering is handled within the eNode B

Physical LayerOverview

Radio Resource Control (RRC)Medium Access Control(MAC)Transport channelsPhysical layerControl / MeasurementsLogical channelsLayer 2Layer 1Radio Link Control (RLC)Layer 3

Physical Layer DetailsThe Layer 1 is defined in a bandwidth agnostic way, allowing the LTE Layer 1 to adapt to various spectrum allocations. The generic radio frame for FDD has a duration of 10ms and consists of 20 slots with a slot duration of 0.5ms. Two adjacent slots form one sub-frame of length 1ms. A resource block spans either 12 sub-carriers with a sub-carrier bandwidth of 15kHz or 24 sub-carriers with a sub-carrier bandwidth of 7.5kHz each over a slot duration of 0.5ms.

Physical Layer Details Contd.The physical channels defined in the downlink are the Physical Downlink Shared Channel (PDSCH), the Physical Downlink Control Channel (PDCCH) and the Common Control Physical Channel (CCPCH). The physical channels defined in the uplink are the Physical Uplink Shared Channel (PUSCH) and the Physical Uplink Control Channel (PUCCH).In addition, signals are defined as reference signals, primary and secondary synchronization signals or random access preambles.The modulation schemes supported in the downlink are QPSK, 16QAM and 64QAM, and in the uplink QPSK, 16QAM and 64QAM. The Broadcast channel use only QPSK

Physical Layer Details Contd.The generic frame structure is applicable to both FDD and TDD. Each radio frame is long and consists of 20 slots of length Tslot= 15360 x Ti = 0,5 ms, numbered from 0 to 19. A sub-frame is defined as two consecutive slots where sub-frame consists of slots and of 20 slots of length , numbered from 0 to 19. The structure of each half-frame in a radio frame is identical. A sub-frame is defined as two consecutive slots where sub-frame consists of slots 2i and 2i+1

Layer 2 and above over the radio interface

Overall architecture

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Layer 2 and above over the radio interfaceThe eNode B hosts the following functions: Functions for Radio Resource Management: Radio Bearer Control, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both uplink and downlink (scheduling);IP header compression and encryption of user data stream;Selection of an MME at UE attachment;

Layer 2 and above over the radio interface: Layer 2 Structure at the eNode B

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Segm.ARQ

Multiplexing UE1

...

Scheduling / Priority Handling

Segm.ARQ

...

Segm.ARQ

Multiplexing UEn

Segm.ARQ

HARQ

HARQ

BCCH

PCCH

Logical Channels

Transport Channels

MAC

RLC

PDCP

ROHC

ROHC

ROHC

ROHC

Radio Bearers

Security

Security

Security

Security

Layer 2 and above over the radio interfaceFor the UE two states are consideredRRC_IDLE where:- UE specific DRX configured by NAS;-Broadcast of system information;-Paging;-Cell re-selection mobility;-The UE shall have been allocated an id which uniquely identifies the UE in a tracking area;-No RRC context stored in the eNode B .RRC_CONNECTED where:-UE has an E-UTRAN-RRC connection;-UE has context in E-UTRAN;-E-UTRAN knows the cell which the UE belongs to;-Network can transmit and/or receive data to/from UE;-Network controlled mobility (handover);- Neighbour cell measurements;-At PDCP/RLC/MAC level:- UE can transmit and/or receive data to/from network;- UE monitors control signalling channel for shared data channel to see if any transmission over the shared data channel has been allocated to the UE;- UE also reports channel quality information and feedback information to eNode B;-DRX/DTX period can be configured according to UE activity level for UE power saving and efficient resource utilization. This is under control of the eNode B

gur11447 - DRX (Discontinuous Reception) Cycle is defined in 3GPP TS 25.304 3.1 as "Individual time interval between monitoring Paging Occasion for a specific UE." 3GPP TS 25.331 8.6.3.1a states "The UE shall determine its idle mode paging occasions and PICH monitoring occasions for that CN domain..., based on the stored CN domain specific DRX cycle length, when using DRX in idle mode." This setting determines the length of the DRX cycle that the UE uses while in idle mode.

Interface towards the Core network

GeneralitiesTwo interfaces:S1-MME for the Control planeS1u for the User plane Additional interface in between eNode Bs: X2Including both Control and User plane

Interface towards the Core network

Interface towards the Core network

The Signaling protocol between eNB and MME is identified by S1-AP S1 Interface Control Plane (eNB-MME)

SCTP

Physical layer

S1-AP

Data link layer

IP

eNode B X2 Interface

This interfaces allows inter-eNode B handover

X2 Interface Control Plane

SCTP

Physical layer

X2-AP

Data link layer

IP

SAE (System Architecture Evolution)To ensure competitiveness of 3GPP systems for the next 10 years and beyondOptimization of the network for IP traffic and its expected growthPerformance improvements reduced latency, higher user data rates, improved system capacity and coverage, and reduced overall cost for the operator. Potential network and traffic cost reduction Flexible accommodation and deployment of existing and new access technologies with mobility by a common IP-based network

3GPP Packet Core Architecture

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