LTE

Simplify the Migration to 4G Networks

by:

Amirali Baha

Outline

• 3G-LTE Introduction

• LTE Architecture

• LTE air-interface

• LTE core

• SAE Architecture

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3GPP Evolution

• 2G: Started years ago with GSM: Mainly voice

• 2.5G: Adding Packet Services: GPRS,EDGE

• 3G: Adding 3G Air Interference: UMTS

• 3G Architecture:• Support of 2G/2.5G and 3G Access

• Handover between GSM and UMTS technologies

• 3G Extensions:• HSDPA/HSPUA

• IP Multi Media Subsystem (IMS)

• Inter-working with WLAN (I-WLAN)

• Beyond 3G:• Long Term Evolution(LTE)

• Introduced in Release 8 of 3GPP in 2004

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Motivation for LTE

• Need for higher data rates• New air interface defined by 3GPP LTE

• Need for high Qos• Use of licensed frequencies to guarantee quality of services

• Need for cheaper infrastructure• Simplify architecture, reduce number of network elements

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Requirements to be met by LTEFast, Efficient, Cheap, Simple

• Peak Data Rates

• Spectrum efficiency

• Reduced Latency

• Mobility

• Spectrum flexibility

• Coverage

• Low complexity and cost

• Interoperability

• Simple packet-oriented E-UTRAN architecture

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LTE/SAE Keywords

• LTE Long Term Evolution

• SAE System Architecture Evolution

• E-UTRAN Evolved UTRAN

• EPC Evolved Packet Core

• eNB Evolved NodeB

• MME Mobility Management Entity

• SGW Serving Access Gateway

• PGW PDN(Packet Data Network)Gateway

• UPE User Plane Entity

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The Next Generation Networks Architecture

• SAE is a study within 3GPP targeting at the evolution of the overall system architecture.

• Object is “ to develop a framework for an evolutionor migration of the 3GPP system to higher-data-rate,lower-latency, packet optimized system that supportsmultiple radio access technologies.”

• This study includes the version of an all-IP networks.

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UMTS 3G LTE

NB: NodeB (base station) RNC: Radio Network ControllerSGSN: Serving GPRS Support NodeGGSN: Gateway GPRS Support Node

eNB: Evolved NodeBP-GW: PDN(Packet Data Network)GatewayS-GW: Serving Access GatewayMME: Mobility Management Entity

LTE Architecture

• The architecture evolution of 3GPP LTE, involves the migration from traditional system to all IP flat network architectures.

• It reduces the number of nodes and distributes the processingload, therefore it reduces the latency.

• The architecture functionality is split into two parts:

• A radio access network (E-UTRAN)

• A core network (EPC)

E-UTRAN: Evolved Universal Terrestrial Radio Access Network

EPC: Evolved Packet Core

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E-UTRAN: UuInterface Roles

• Supports all services including real-time multimedia services

• It contains new network elements called enhanced NodeBs (eNBs)

• The function of eNBs includes all radio interface –related functions

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As(Uu)Functions

• Radio Bearer management• Radio Channel • Ciphering• Radio Mobility (HO)

Air InterfaceEnabling Technologies

• LTE aims at better spectral flexibility, higher data rates, low latency and improved coverage.

• To achieve the targets, LTE employs the enabling technologies:

• OFDMA

• SC-FDMA

• MIMO

• LTE employs OFDMA for downlink and SC-FDMA for uplink transmission.

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Orthogonal Multiple Access Schemes

• Downlink: OFDMA

• The available spectrum is divided into multiple carriers, called sub-carriers, which are orthogonal to each other.

• sub-carriers are allocated dynamically among the different users.

• Each of these subcarriers is independently modulated by low rate data stream.

• OFDM has several benefits:

• High spectral efficiency

• Robust against frequency- selective and multi- path fading

• Supports flexible bandwidth deployment

• Facilitates frequency- domain scheduling

• Well suited to advanced MIMO techniques

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Orthogonal Multiple Access Schemes

• Uplink: SC-FDMA

• SC-FDMA is chosen because it combines the low Peak-to-average Power Ratio (PAPR) techniques of single-carrier transmission systems, such as CDMA, with the multipath resistance and flexible frequency allocation of OFDMA.

SC-FDMA has several benefits:

• Based on OFDMA with DFT precoding

• Common structure of transmission resources compared to downlink

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Single-Carrier Frequency Division Multiple Access(SC-FDMA)

• The incoming bit stream is first converted to single-carrier symbols.

• Then, data symbols in the time domain are converted to the frequency domain(Discrete Fourier Transform).

• Then, data symbols mapped to the desired band in the overall channel bandwidth.

• Now, they back to the time domain using Inverse Fourier Transform.

• Finally, the Cyclic Prefix is inserted. It’s used for effectively eliminate Inter Symbol Interference

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cyclic prefix refers to the prefixing ofa symbol with a repetition of theend. Although the receiver istypically configured to discard thecyclic prefix samples, the cyclic prefixserves as a guard interval.

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Multiple Antenna Schemes in LTE

• In DL: Tx diversity, Rx diversity, spatial multiplexing supported

(2×2,4×2 configurations).

• In UL: Only 1 Transmitter (antenna selection Tx diversity), Rx

diversity with 2 or 4 antennas at eNB supported.

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EPC (Evolved Packet Core)

• The EPC consist of functional entities:

• MME (Mobile Management Entity)

• Manages mobility, UE identity, and security parameters

• S-GW (Serving-Gateway)

• Node that terminates interface toward e-UTRAN

• P-GW (Packet Data Network-Gateways)

• Node that terminates the interface towards PDN (Packet Data Network)

• PCRF (Policy and charging Rules Function)

• Controls the charging and the IP Multimedia Subsystem configuration

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E-UTRAN EPC

Integrated EPC Network Functions

• As mobile operators evolve to LTE, they will benefit from solutionsthat can integrate 2G/3G and 4G functions in a single nodeproviding separate access through a common multimedia core.

• Support for multiple network technologies and the correspondingmultimedia core network functionality in a multi-access, multi-service environment.

GERAN: GSM EDGE Radio Access NetworkIMS: IP Multimedia SubsystemHSS: Home Subscriber ServerSGSN: Serving GPRS Support Node

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LTE ArchitectureAn overview

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SAE (System Architecture Evolution)

Objectives

• New network architecture to support the high- throughput and low-latency LTE access system• Simplified network architecture

• All IP network

• Support mobility between multiple heterogeneous access system• 2G/3G, LTE, non 3GPP access system such as WLAN, WiMAX

• Inter-3GPP handover

• Inter-3GPP and non-3GPP mobility

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SAE Architecture (Baseline)

Red indicates new functional element/Interface

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IASA Inter-Access System Anchor

SAE Architecture (Functions per Element)

• MME (Mobility Management Entity)

• UPE (User Plane Entity)• Packet routing and forwarding

• 3GPP anchor• Mobility anchor between 2G/3G and LTE

• SAE anchor• Mobility anchor between 3GPP and non 3GPP

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SAE Architecture (Interfaces)

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SAE Architecture (Interfaces)

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Conclusion

• The 3GPP LTE/SAE is a future-oriented radio accesssystem designed to support huge traffic of futureend user requirements like high speed internet, DVB-H

• The 3GPP LTE provides a framework forstandardization in the evolution towards 4G.

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