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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