1LTE.Introduction & Architecture (2)

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LTE Introduction, Introduction to EPS & EPS Network Architecture


LTE is the latest standard in the mobile network technology tree that previously realized the GSM/EDGE and UMTS/HSDPA network technologies that now account for over 85% of all mobile subscribers. LTE will ensure 3GPP’s competitive edge over other cellular technologies.

Goals include :

Significantly increase peak data rates, scaled linearly according to spectrum allocation

improving spectral efficiency

lowering costs

improving services

making use of new spectrum opportunities

Improved quality of service

better integration with other open standards

LTE Introduction


Peak data rate

• Goal: significantly increased peak data rates, scaled linearly according to spectrum allocation

• Targets: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)

LTE Introduction


Spectrum issues

• Spectrum flexibility

E-UTRA to operate in 1.25, 1.6, 2.5, 5, 10, 15 and 20 MH allocations…hence allowing different possibilities for re-framing already in use spectrum

- uplink and downlink

- paired and unpaired

• Co-existence

- with GERAN/3G on adjacent channels

- with other operators on adjacent channels

- with overlapping or adjacent spectrum at country borders

- Handover with UTRAN and GERAN

- Handover with non 3GPP Technologies (CDMA 2000, WiFi, WiMAX)

LTE Introduction


• Peaks rates: DL 100Mbps with OFDMA, UL 50Mbps with SC-FDMA

• Latency for Control-plane < 100ms, for User-plane < 5ms

• Optimised for packet switched domain, supporting VoIP

• Scaleable RF bandwidth between 1.25MHz to 20MHz

• 200 users per cell in active state

• Supports MBMS multimedia services

• Uses MIMO multiple antenna technology

• Optimised for 0-15km/h mobile speed and support for up-to 120-350 km/h

• No soft handover, Intra-RAT handovers with UTRAN

• Simpler E-UTRAN architecture: no RNC, no CS domain, no DCH

LTE Requirements

LTE Introduction


• Release 99 (2000): UMTS/WCDMA

• Release 5 (2002) : HSDPA

• Release 6 (2005) : HSUPA, MBMS(Multimedia Broadcast/Multicast Services)

• Release 7 (2007) : DL MIMO, IMS (IP Multimedia Subsystem), optimized real-time services (VoIP, gaming, push-to-talk).

• Release 8(2009?) :LTE (Long Term Evolution)

Long Term Evolution (LTE)

• 3GPP work on the Evolution of the 3G Mobile System started in November 2004.

• Currently, standardization in progress in the form of Rel-8.

• Specifications scheduled to be finalized by the end of mid 2008.

• Target deployment in 2010.

3GPP Evolution

LTE Introduction


Evolution of Radio Access Technologies

LTE Introduction


Multiple access scheme• Downlink: OFDMA

• Uplink: Single Carrier FDMA (SC-FDMA)

Adaptive modulation and coding• DL modulations: QPSK, 16QAM, and 64QAM

• UL modulations: QPSK and 16QAM

• Rel-6 Turbo code: Coding rate of 1/3, two 8-state constituent encoders, and a contention- free internal inter leaver.

• Bandwidth scalability for efficient operation in differently sized allocated spectrum bands

• Possible support for operating as single frequency network (SFN) to support MBMS

Key Features of LTE

LTE Introduction


• Multiple Antenna (MIMO) technology for enhanced data rate and performance.

• ARQ within RLC sub layer and Hybrid ARQ within MAC sub layer.

• Power control and link adaptation

• Implicit support for interference coordination

• Support for both FDD and TDD

• Channel dependent scheduling & link adaptation for enhanced performance.

• Reduced radio-access-network nodes to reduce cost , protocol-related processing time & call setup time.

Key Features of LTE

LTE Introduction


• LTE has been designed to support only packet switched services, in contrast to the circuit-switched model of previous cellular systems.

• LTE aims to provide seamless Internet Protocol (IP) connectivity between User Equipment (UE) and the Packet Data Network (PDN), without any disruption to the end users applications during mobility.

• The term ‘LTE’ encompasses the evolution of the radio access through the Evolved-UTRAN(E-UTRAN), it is accompanied by an evolution of the non- radio aspects under the term ‘System Architecture Evolution’ (SAE) which includes the Evolved Packet Core (EPC) network. Together LTE and SAE comprise the Evolved Packet System (EPS).

EPS = EPC + E-UTRAN

Evolved Packet System (EPS) Introduction


Evolved Packet System (EPS) Network Architecture


EPS uses the concept of EPS bearers to route IP traffic from a gateway in the PDN to the UE. A bearer is an IP packet flow with a defined Quality of Service (QoS) between the gateway and

the UE. The E-UTRAN and EPC together set up and release bearers as required by applications.

SGSN

GPRS Core

3GPPanchor

SAEanchor

MMEUPE

Operator’sIP Services

(e.g. IMS, PSS, etc,)

eNB

eNB eNB

eNB

Evolved RAN (LTE)

GERAN

UTRAN

Trusted non 3GPPIP Access

EPDG

WLANAccess Network

EPC (SAE)

IASA

GB

Iu

S3

S4S7

Rx+

S5a S5bS1

S2a

S2b

SGi

S6

WLAN 3GPP

IP Access



System Architecture Evolution (SAE) is the core network architecture of 3GPP's future LTE wireless communication standard.

SAE is the evolution of the GPRS Core Network, with some differences.

The main principles and objectives of the LTE-SAE architecture include :

• A common anchor point and gateway (GW) node for all access technologies

• IP-based protocols on all interfaces;

• Simplified network architecture

• All IP network

• All services are via Packet Switched domain

• Support mobility between heterogeneous RATs, including legacy systems as GPRS, but also non-3GPP systems (say WiMAX)

• Support for multiple, heterogeneous RATs, including legacy systems as GPRS, but also non-3GPP systems (say WiMAX)

System Architecture Evolution (SAE)



MME (Mobility Management Entity):• Manages and stores the UE control plane context, generates temporary Id, provides

UE authentication, authorization, mobility management

UPE (User Plane Entity):• Manages and stores UE context, ciphering, mobility anchor, packet routing and

forwarding, initiation of paging

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

SAE anchor:• -Mobility anchor between 3GPP and non 3GPP (I-WLAN, etc)

Evolved Packet Core(EPC)


• MME(Mobility management entity).

• S-GW(Serving gateway).

• P-GW( packet data network gateway).

• HSS(Home subscriber server ).

• PCRF(policy & charging resource or rules function).

EPC Key Nodes


Mobility management entity(MME)

• It handles signalling functionality, it manages mobility.

• MME tracks & maintains the current location of UEs.This allows MME to page a mobile.

• It is also involved in MME selection for inter MME handovers,S10 interface between MME’S provides MME relocation & MME to MME information transfer.

• MME selects SGSN & Performs inter CN nodes signalling for inter 3GPP handovers

• MME manages UE identities & security related parameters

• It also plays a vital role in user authentication & for that it consults HSS on S6a interface which enables transfer of subscription & authentication data to MME

• Based on subscription data MME selects PDN GW & then SGW & finally establishes a bearer between UE & PDN-GW.

EPC Key Nodes


EPC Key Nodes


Serving Gateway(S-GW)

• It is basically define to handle user data functionality & is involved in routing & forwarding of data packet to P-GW via S5.

• S5 interface can be GTP based or PMIP based & is also used for S-GW relocation due to UE mobility.

• S-GW is connected to eNB via S1-U interface which provides user plane tunneling & inter-eNB handovers.

• S-GW performs mobility anchoring for Inter-3GPP mobility on S4 interface which connects S-GW & 2.5/3G SGSN.

• S-GW is also responsible for Lawful Interception,accouting on user.

• A many-to-many S1 interface provided between the eNBs & MME/S-GW supports redundancy/load sharing of network nodes.

• Load sharing of MMEs enables mobility of aUE with in a geographical area without changing the MME.

EPC Key Nodes


EPC Key Nodes


Packet data network gateway(P-GW)

• The PDN Gateway is the node that connects the UE to external PDN’S & as the UE’s default router.

• A UE may be connected to multiple PDNs through one or more PDN Gateway.

• A PDN-GW is responsible for anchoring the user plane mobility within the LTE/EPC network as well as for inter-RAT handovers.

• A PDN-GW function as a mobile IP Home Agent(HA)when interworking between LTE & non-3GPP access network such as EVDO & WIMAX.

• The PDN Gateway may be responsible for the allocation of an IP address to the UE during default EPS bearer setup. Packet filtering of user traffic may be implemented at P-GW in support of QOS differentiation between multiple IP flows.

• The S7 interface provides transfer of(QOS)policy & charging rules from the policy(PCRF) to P-GW.The policy rules indicate whether the P-GW Should grant resource reservation request & if it is allowed to process packets for given IP flow

EPC Key Nodes


EPC Key Nodes


Home subscriber server (HSS)

• HSS is a user data base that stores subscription related information to support other call control & session management entities.

• It is storehouse for user identification, numbering & service profile. It is mainly involved in user authentication & authorization.

• During registration MME talks to HSS via S6a interface for user authentication & ciphering. The HSS generates security information for mutual authentication, integrity check& ciphering & can also provide information about the user physical location.

EPC Key Nodes


Policy & Charging Rule Function

• The PCRF functionalities include policy control decision & flow based charging control.PCRF is the main QOS control entity in the network.

• It is responsible for building the policy rules that will apply to user services & passing the rules to the PDN-GW via S7 interface.

• The PCRF may use the subscription information as basic for the policy & charging control decision.

EPC Key Nodes


E-UTRAN Architecture


The evolved UTRAN (eUTRAN) architecture consist of eNBs(evolved Node Bs).

Functions of eNodeB :

• Terminates RRC, RLC and MAC protocols and takes care of Radio Resource Management functions :

-Controls radio bearers

-Controls radio admissions

-Controls mobility connections

-Allocates radio resources dynamically (scheduling)

-Receives measurement reports from UE

• Selects MME at UE attachment

• Schedules and transmits paging messages coming from MME

• Schedules and transmits broadcast information coming from MME & O&M

• Decides measurement report configuration for mobility and scheduling

• Does IP header compression and encryption of user data streams

E-UTRAN


E-UTRAN


E-UTRAN


EPS Bearer service and NAS Signalling Connection

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1LTE.Introduction & Architecture (2)