doc5-lte workshop tun session4 network architecture

ITU/BDT Arab Regional Workshop on “4G Wireless Systems” -Tunisia 2010

/ b l k hITU/BDT Arab Regional Workshop on“4G Wireless Systems”4G Wireless Systems

LTE Technology

Session 4 : Network Architecture

Speakers M. Lazhar BELHOUCHETM Hakim EBDELLIM. Hakim EBDELLI

Date 27 – 29 January 2010

www.cert.nat.tn1 Network Architecture


Agenda

• Introduction

• Evolved Packet System (EPS) Architecture ‐Subsystems

• Network Architecture Evolution

LTE/SAE N k El• LTE/SAE Network Elements

• LTE/SAE Network Interfaces/



Introduction• LTE/SAE architecture is driven by the goal to

optimize the system for packet data transfer.• No circuit switched components

IMS/PDN

• New approach in the inter-connection between radio access network and core network

• The EPS architecture is made up of an EPC (Packet k l f d ) d

EPCCore Network, also referred as SAE) and an eUTRAN Radio Access Network (also referred as LTE)

• The CN provides access to external packet IPeUTRAN

• The CN provides access to external packet IP networks and performs a number of CN related functions (e.g. QoS, security, mobility and terminal context management) for idle (camped) and active LTE-UEterminals

• The RAN performs all radio interface related functions

EPS


EPS


Evolved Packet System (EPS) Architecture -Subsystems

E-UTRAN SAE or EPC



Network Architecture EvolutionDirect tunnel I-HSPAHSPA R7 HSPA R7 LTE R8

HSPAHSPA R6

LTE

SAE GWGGSN

SGSN

GGSN

SGSN MME/SGSN

GGSN

SGSN SGSN

RNC

SGSN MME/SGSNSGSN

RNC

Node B (NB)

Node B + RNC

Functionality

Evolved Node B (eNB)

Node B (NB)

User planeControl Plane

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Control Plane

Network Architecture


Network Architecture Evolution – Cont.

Internet

3GPP Rel 6 / HSPA

Node B RNC SGSN GGSN

− Original 3G architectureUser plane− Original 3G architecture.

− 2 nodes in the RAN.− 2 nodes in the PS Core Network.

Control Plane

− Every Node introduces additional delay.− Common path for User plane and Control plane data.− Air interface based on WCDMA.Air interface based on WCDMA.− RAN interfaces based on ATM.− Option for Iu-PS interface to be based on IP.




3GPP Rel 7 / Internet HSPA

Internet

SGSNGGSN

Direct tunnel

InternetNode B

(RNC Funct.) User planeUser planeControl Plane− I-HSPA introduces the first true flat architecture to WCDMA.

− Standardized in 3GPP Release 7 as Direct Tunnel with collapsed RNC.M t t f th RNC f ti liti d t th N d B− Most part of the RNC functionalities are moved to the Node B.

− Direct Tunnels runs now from the GGSN to the Node B.− Solution for cost-efficient broadband wireless access.− Improves the delay performance (less node in RAN).− It can be deployable with existing WCDMA base stations.

Transmission savings

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− Transmission savings




3GPP Rel 8 / LTE MMESAE GW

Direct tunnel

Internet

Evolved Node BUser plane

LTE takes the same Flat architecture from Internet HSPA

User planeControl Plane

LTE takes the same Flat architecture from Internet HSPA.Air interface based on OFDMA.All-IP network.New spectrum allocation (i.e 2600 MHz band)Possibility to reuse spectrum (i.e. 900 MHZ)


y ( )


LTE/SAE Network ElementsEvolved UTRAN (E-UTRAN) Evolved Packet Core (EPC)

HSS

S10

S6a

MME: Mobility Management Entity

PCRF:Policy & Charging Rule Function

LTE-UE

MME S10

S11

S1-MME PCRF

S7Rx+Evolved

Node B(eNB)

X2

ServingGateway

S1-U

PDNGateway

PDNSGiS5/S8

cellLTE-Uu

Main references to architecture in 3GPP specs.: TS23 401 TS23 402 TS36 300

Gateway Gateway

SAEGateway

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TS23.401,TS23.402,TS36.300



EvolvedLTE U

LTE-UEEvolved Node B (eNB)

Inter-cell RRM: HO, load balancing between cells

Radio Bearer Control:setup , modifications and release of Radio Resources

eNB FunctionsEvolvedNode B(eNB)cell

LTE-Uu

release of Radio Resources

Connection Mgt. Control: UE State Mgmt. MME-UEConnectionRadio Admission Control

− It is the only network element defined as part of EUTRAN. It replaces the old Node B / RNC combination

eNode B Measurements Collection and evaluation

Dynamic Resource Allocation (Scheduler)

IP Header Compression/ de-compression

− It replaces the old Node B / RNC combination from 3G.

− It terminates the complete radio interface including physical layer.

Access Layer Security: ciphering and integrity protection on the radio interface

MME Selection at Attach of the UE

− It provides all radio management functions− An eNB can handle several cells. − To enable efficient inter-cell radio

User Data Routing to the SAE GW.

Transmission of Paging Message coming from MME

Transmission of Broadcast Info(System info, MBMS)

management for cells not attached to the same eNB, there is a inter-eNB interface X2 specified. It will allow to coordinate inter-eNB handovers without direct involvement of EPC

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during this process.



MME Functions

Control plane NE in EPCMobility Management Entity (MME)

EvolvedNode B(eNB) MMES1-MME

HSS

S6a

Non-Access-Stratum (NAS)Security (Authentication,integrity Protection)

Idle State Mobility Handling

ServingGateway

S1-US11

S6a Idle State Mobility Handling

Tracking Area updates

Subscriber attach/detach

Radio Security Control

Signalling coordination for SAE Bearer Setup/Release− It is a pure signaling entity inside the EPC.

− SAE uses tracking areas to track the position of idle UEs. The basic principle is identical to location or routing areas from 2G/3G.

Trigger and distribution of Paging Messages to eNB

Roaming Control (S6a interface t HSS)

− MME handles attaches and detaches to the SAE system, as well as tracking area updates

− Therefore it possesses an interface towards the HSS (home subscriber server) which stores the subscription relevant information and the

tl i d MME i it t d t b to HSS)

Inter-CN Node Signaling (S10 interface), allows efficientinter-MME tracking area updatesand attaches

currently assigned MME in its permanent data base.− A second functionality of the MME is the signaling coordination to setup

transport bearers (SAE bearers) through the EPC for a UE.− MMEs can be interconnected via the S10 interface

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and attaches



EvolvedNode B

MME

Serving SAE Gateway

(eNB) MME

S1-U

S1-MME

S5/S8S11

S6a

Serving Gateway Functions

Serving SAEGateway

PDNGateway

Local mobility anchor point:Switching the user plane path to a new eNB in case of Handover

Serving Gateway Functions

− The serving gateway is a network element that manages the user data path (SAE bearers) within EPC.

− It therefore connects via the S1-U interface towards eNB d i li k k t d t f h d t it

Mobility anchoring for inter-3GPP mobility. This is sometimes referredto as the 3GPP Anchor function

and receives uplink packet data from here and transmits downlink packet data on it.

− Thus the serving gateway is some kind of distribution and packet data anchoring function within EPC.

Idle Mode Packet Buffering and notification to MME

Packet Routing/Forwardingpacket data anchoring function within EPC.− It relays the packet data within EPC via the S5/S8

interface to or from the PDN gateway.− A serving gateway is controlled by one or more MMEs via

S11 i t f

between eNB, PDN GW and SGSN

Lawful Interception support

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S11 interface.



Packet Data Network (PDN) SAE Gateway

MME PCRFS7 Rx+

S11S6a

PDN Gateway Functions

Mobility anchor for mobility between 3GPP access systems and non-3GPPaccess systems This is sometimes

ServingGateway

S5/S8

PDN SAEGateway

PDNSGi

Policy Enforcement (PCEF)

Per User based Packet Filtering (i e

access systems. This is sometimes referred to as the SAE Anchor function

− The PDN gateway provides the connection between EPC and a number of external data networks

Gateway Gateway Per User based Packet Filtering (i.e. deep packet inspection)

Charging & Lawful Interception support

EPC and a number of external data networks. − Thus it is comparable to GGSN in 2G/3G networks.− A major functionality provided by a PDN gateway is the

QoS coordination between the external PDN and EPC.

IP Address Allocation for UE

Packet Routing/Forwarding betweenServing GW and external Data Network

− Therefore the PDN gateway can be connected via S7 to a PCRF (Policy and Charging Rule Function).

Se g G a d e te a ata et o

Packet screening (firewall functionality)



Policy and Charging Rule Function (PCRF)

MME

S5/S8 SGi

PCRFS7 Rx+

S11S6a

PCRF: Policy & Charging Rule Function

QoS policy negotiation with PDN

ServingGateway

S5/S8

PDN SAEGateway

PDNSGi

Charging Policy: determines how packets should be accounted

Q p y g

− The PCRF major functionality is the Quality of Service (QoS) coordination between the external PDN and EPC.( )− Therefore the PCRF is connected via Rx+ interface to the external Data network (PDN)− This function can be used to check and modify the QoS

i t d ith SAE b t f SAE t tassociated with a SAE bearer setup from SAE or to request the setup of a SAE bearer from the PDN. −This QoS management resembles the policy and charging control framework introduced for IMS with UMTS release 6.

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co o a e o oduced o S U S e ease 6



Home Subscriber Server (HSS)

Permanent and central subscriberdatabase

HSS Functions

MME

HSS

S6a

− The HSS is already introduced by UMTS release 5

Stores mobility and service data for every subscriber

S6a

Contains the Authentication Centerrelease 5.− With LTE/SAE the HSS will get additionally data per subscriber for SAE mobility and service handling

Contains the Authentication Center(AuC) functionality.

handling. −Some changes in the database as well as in the HSS protocol (DIAMETER) will be necessary to enable HSS for LTE/SAE. to enable HSS for LTE/SAE. −The HSS can be accessed by the MME via S6a interface.



LTE/SAE Network InterfacesEvolved UTRAN (E-UTRAN) Evolved Packet Core (EPC)

HSS

S6aMME: Mobility Management Entity

LTE-UEMME S10

S1-MME PCRF

S7Rx+Evolved

Node B(eNB)

X2

S i

S1-U

S11

PDN

PDNSGiS5/S8

(eNB)

cell

LTE U SAEServingGateway

PDNGateway

LTE-Uu SAEGateway

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User plane Control Plane Control Plane + User plane



LTE Radio Interface and the X2 InterfaceLTE-Uu

f f(E)-RRC User PDUs User PDUs..

Air interface of EUTRAN Based on OFDMA in downlink and SC-FDMA in uplinkFDD and TDD duplex methodsScalable bandwidth 1 4MHz to currently 20 MHz

(E) RRC User PDUs User PDUs

PDCP (ROHC = RFC 3095)

RLC

MACTS 36.300

Scalable bandwidth 1.4MHz to currently 20 MHzData rates up to 100 Mbps in DL MIMO (Multiple Input Multiple Output) is a major component although optional.

L )LTE-L1 (FDD/TDD-OFDMA/SC-FDMA)

eNBLTE-Uu

X2Inter eNB interfaceHandover coordination without involving the EPC

User PDUs

X2-UP(User Plane)

X2-CP(Control Plane)

Handover coordination without involving the EPCX2AP: special signalling protocolDuring HO, Source eNB can use the X2 interface to forward downlink packets still buffered or arriving from th i t t th t t NB

X2GTP-U

UDP

IPTS 36.424

X2-AP

SCTP

IPTS 36.422

TS 36.423

the serving gateway to the target eNB.This will avoid loss of a huge amount of packets during inter-eNB handover.eNB

L1/L2L1/L2TS 36.421 TS 36.421

TS 36.420[ tl l i TS 36 300 §20]

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[currently also in TS 36.300 §20]



S1‐MME & S1‐U InterfacesS1-MMEC t l i t f b t NB d MME S1 MMEControl interface between eNB and MMES1flex allows 1 eNB to connect to several MME MME and UE will exchange non-access stratum signaling via eNB through this interface. MME

S1-MME(Control Plane)

NAS Protocols

S1-APTS 36.413g g gE.g.: if a UE performs a tracking area update the TRACKING AREA UPDATE REQUEST message will be sent from UE to eNB and the eNB will forward the message via S1-MME to the MME.

SCTP

IP

L1/L2 TS 36.411

TS 36.412

S1AP:S1 Application Protocol

S1-UUser plane interface between eNB and serving

S1-U(User Plane)

User PDUseNBgateway.It is a pure user data interface (U=User plane).S1flex-U also supported: a single eNB can connect to several Serving GWs.

ServingGateway

GTP-U

UDP

IP

TS 36.414

gWhich Serving GW a user’s SAE bearer will have to use is signaled from the MME of this user.

L1/L2TS 36.411

TS 36.410

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[currently in TS 36.300 §19]



EUTRAN & EPC connected with S1‐flex

Several cases

1 eNB 1 Single S1-MMESingle S1-U

2 eNB 2 Single S1-MMEMultiple S1-U S1Flex-U

3

eNB 3 Multiple S1-pMME S1Flex

Single S1-U



S10 & S6a Interfaces

HSS

S6a Candidate(Control Plane)

S6a Appl.

DIAMETER

S10 Candidate(Control Plane)

GTP-CMME HSS

SCTP

IP

L1/L2

DIAMETERMME UDP

IP

L1/L2 L1/L2

TR 29.801TR 29.801S10Interface between different MMEs

S6aInterface between the MME and the HSS

Used during inter-MME tracking area updatesThe new MME can contact the old MME the user had been registered before to retrieve data about identity (IMSI), security information (security context,

The MME uses it to retrieve subscription information from HSS (handover/tracking area restrictions, external PDN allowed, QoS, etc.) during attaches and updates( ), y ( y ,

authentication vectors) and active SAE bearers (PDN gateways to contact, QoS, etc.)Obviously S10 is a pure signaling interface, no user data runs on it.

The HSS can during these procedures also store the user’s current MME address in its database.



S11 & S5/S8 Interfaces S5/S8Interface between Serving GW and PDN GWS5 If S i GW d PDN GW b l t th

MME

S11 Candidate

S11Interface between MME and a Serving GWA single MME can handle multiple Serving GW each one with its own S11 interfaceU d t di t th t bli h t f SAE

S5: If Serving GW and PDN GW belong to the same network (non-roaming case)S8:If this is not the case (roaming case)S8 = S5 + inter-operator security functionsMainly used to transfer user packet data between PDN GWS11 Candidate

(Control Plane)

UDP

GTP-C

Used to coordinate the establishment of SAE bearers within the EPCSAE bearer setup can be started by the MME (default SAE bearer) or by the PDN Gateway.

Mainly used to transfer user packet data between PDN GWand Serving GWSignaling on S5/S8 is used to setup the associated bearer resources S5/S8 can be implemented either by reuse of the GTP

S5/S8 GTP Candidates(Control and User Plane)

IP

L1/L2S5/S8 IETF Candidates

(Control and User Plane)

p yprotocol from 2G/3G or by using Mobile IPv6 with some IETF enhancements.

ServingGateway

PDNGateway

Sgi

(Control and User Plane)User PDUs

GTP-U

UDP

GTP-C

TR 29.801(Control and User Plane)

User PDUs

MIPv6 Tunneling

Layer

PMIPv6

IPv6PDN

SgiUDP

IP

L1/L2

yLayerIPv4/IPv6

L1/L2

IPv4

IPv6

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TS 23.401 / TR 29.801 TS 23.402 / TR 29.801



S7 & SGi IntefacesPCRF

S7 (Control Plane)??

S7Interface between PDN GW and PCRF (Policy and Charging Rule Function)

SGi(User Plane)

??

IP

L1/L2

It allows:−the PCRF to request the setup of a SAE bearer with appropriate QoS−allows the PDN GW to ask for the QoS of

PDNGateway

IMS/PDNApplication

UDP or TCPUDP or TCP

IPv4/IPv6

TR 23.401

allows the PDN GW to ask for the QoS of an SAE bearer to setup−to indicate EPC status changes to the PCRF to apply a new policy rule. SGi

Interface used by the PDN GW to send and receive data to

GatewayL1/L2

Interface used by the PDN GW to send and receive data to and from the external data networkIt is typically either IPv4 or IPv6 basedDownlink data coming from the external PDN must be assigned to the right SAE bearer of the right user by analysisassigned to the right SAE bearer of the right user by analysis of the incoming packet’s IP addresses, port numbers, etc.This interface corresponds to the Gi interface in 2G/3G networks



Rx+ Interface

Rx+(Control Plane)

S7 ??

PCRF ??

IP

L1/L2

SGi

TR 23.203

R +

PDNGateway

PDN

Rx+Interface between PCRF(Policy & Charging Rules Function) and the external PDN network/operators IMSStandardized in 3GPP TS 23 203

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Standardized in 3GPP TS 23.203.



SAE/LTE Interworking with 2G/3G Networks

SGSN

I PS

GERANGb

Gr

GGSNGnPDN

Gi

HSSS3UTRAN

Iu-PSS4

MME

S6a

S7NBLTE-UE

S1-U

S11S1-MME

PDN

PCRF

S7Rx+

SGiS5/S8

eNB

cell

Evolved UTRAN (E UTRAN)

ServingGateway

PDNGateway

PDNcellLTE-Uu

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Evolved UTRAN (E-UTRAN) Evolved Packet Core (EPC)



S4(U Pl )S3

S3 & S4 Interfaces (User Plane)S3

(Control Plane)

UDP

GTP-CGTP-U

User PDUs

SGSNUDP

IP

L1/L2

UDP

IP

L1/L2

MMEServing

Gateway

TR 29.801 / TS 23.401TR 29.801 / TS 23.401

MME Gateway

S3/S4Interfaces between EPC and 2G/3G packet switched core network domainThey would allow inter-system changes between SAE and 2G/3Gey ou d a o te syste c a ges bet ee S a d G/3GThe S3 is a pure signalling interface used to coordinate the inter-system change between MME and SGSNThe S4 is the user plane interface and it is located between SGSN and Serving SAE GW.This would allow to either forward packet data from EUTRAN via Serving SAE GW to SGSN (and then to GGSN) f 2G/3G RAN t SGSN t S i SAE GW t PDN GW

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GGSN) or from 2G/3G RAN to SGSN to Serving SAE GW to PDN GW.



SAE/LTE Interworking with 3G ‐ Alternative

SGSNGERANGb

Gr

GGSNGnPDN

Gi

HSSS3S4UTRAN

Iu-PSGr

Direct Tunnels from Serving GW to RNC

MME

S6a

S12

Serving GW to RNC (User Plane)

MME

S1 U

S11S1-MME PCRF

S7Rx+

SGiS5/S8

eNB

ServingGateway

S1-U

PDNGateway

PDNSGiS5/S8cellLTE-Uu

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Evolved UTRAN (E-UTRAN) Evolved Packet Core (EPC)Network Architecture


S12 InterfaceS12

GTP-UUser PDUs

S12(User Plane)

ServingGateway

UDPIP

L1/L2

UTRAN

S12Interfaces between EPC and 3G Radio access network

It ld ll i t t h b t SAE d 3G

TR 29.801 / TS 23.401

It would allow inter‐system changes between SAE and 3G

The S12 is the user plane interface used for tunneling user data directly between the Serving SAE GW and the UTRAN.

This would allow to forward packet data from 3G RAN to Serving SAE GW to PDN GWThis would allow to forward packet data from 3G RAN to Serving SAE GW to PDN GW.

It is based on the Gn interface between the SGSN and the GGSN and so uses the GTP‐U protocol.



LTE/SAE Roaming Architecture – Case 1

PCRFRx+

HSS

Home PLMNPDN

GatewayIMS/PDN

PCRF

S7

SGi

Case 1:S8S6a

hPLMN

Visited PLMNvPLMN Case 1:

Home Routed TrafficBy connecting Serving GW in vPLMN to PDN GW in

MME

S11S1-MMEeNB

vPLMN

hPLMNGTP tunnel and MIPv6 options over the S8 interface

ServingGateway

S1-UcellLTE-Uu

interfaceAlso called “Remote Breakout”.




LTE/SAE Roaming Architecture – Case 2Case 2: “Local Breakout”Case 2: Local Breakout UE can access the PDN network directly from the vPLMN rather than traffic being routed through the hPLMN. Breakout should depend on the service:i e :internet access local breakout

HSS

Home PLMNi.e.:internet access local breakouti.e.:access to corporate VPN remote breakoutS9: PCRF-to-PCRF interface: roaming controlled by hPLMN policies

Home PLMNhPLMNhPCRF

S6aVisited PLMNvPLMN

S9

MME

S

S11S1-MME

eNB vPCRF

S7

Rx+

SGiS5

ServingGateway

S1-UcellLTE-Uu PDN

Gateway

IMS/PDNSGiS5

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S9 Interface

??

S9(Control Plane)

??

IP

??

hPCRF vPCRF

IP

L1/L2

TR 29 801 / TS 23 401???????

S9

Interfaces between the hPCRF and the vPCRFused in roaming cases.

TR 29.801 / TS 23.401???????

It is used enforcement in the VPLMN of dynamic control polices from the HPLMN.



LTE/SAE Interworking with Non‐3GPP AccessEvolved UTRAN (E-UTRAN) Evolved Packet Core (EPC)Evolved UTRAN (E UTRAN)

HSSeNB

MMES6a

S1 U

S1-MMEPCRF

S7Rx+

cellLTE-Uu

Common GW for all accesses• Generic support for any non-3GPP access Serving

Gateway

S1-U S11

PDNGateway

PDNSGiS5

SAEG t(e.g. WLAN, Fixed)

• Session Mobility using Mobile IP• Policy control supported for non-3GPP accesses

A th ti ti f 3GPP

Gateway GatewayGateway

S2• Access authentication for non-3GPPaccesses using Authentication, Authorization and accounting (AAA) mechanisms• Security support for non-trusted accesses

Non-3GPP Access:WiMAx, WLAN, Fixed,….

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y pp



Accounting and Charging in SAE/LTE Networks

− It will be an evolution of the PS Domain charging mechanisms for GPRS and UMTS

− It will facilitate seamless interworking with legacy charging systems.

− The charging filter rules are provided by the PolicyThe charging filter rules are provided by the Policy and Charging Rule Function (PCRF).

− The IMS Charging Function provides information about the user’s session (e g call controlabout the user s session (e.g. call control, multimedia, services).

− The Application Charging Function provides f b h f h ’ ffinformation about the content of the user’s traffic

(e.g. URL, file or media stream name).



Factors affecting the price of a user session

− Usage time or duration.

− Transferred data volume

− Number of events (units)

− Destination of session

− Location and time zone of session origination

− Quality of Service (QoS)Q y (Q )

− Radio Access Technology (RAT, e.g. LTE and 3G/2G in the case of handover, non 3GPP access)non‐3GPP access)

− Tariff Time

− User identification



Thanks for your AttentionThanks for your Attention


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