The 3GPP2 Architecture

Sridhar Machiraju

CS294-3, Spring 2002,

University of California at Berkeley

Contents

• Introduction• The 3GPP2 Architecture• Mobility Management in 3GPP2• Functional comparison of 3GPP and

3GPP2.• Architectural comparison of 3GPP and

3GPP2• The MWIF Architecture.

We saw that the 3GPP architecture evolved from the already-existing GPRS network. It

can be viewed as IP-based multimedia enhancements to 2G networks.

However, 3GPP2 has created a new architecture (there was no existing packet

packet data service) for the 2G and 3G CDMA air interfaces.

Introduction

Contents

• Introduction• The 3GPP2 Architecture• Mobility Management in 3GPP2• Functional comparison of 3GPP and

3GPP2.• Architectural comparison of 3GPP and

3GPP2• The MWIF Architecture.

Basic Design Philosophy of 3GPP2

• Leverage existing globally-accepted IETF protocols whenever possible e.g., mobile IP (for mobility), IPSec (for e2e security), AAA (authentication, authorization and accounting for network access).

• Some advantages are – – Interoperability/roaming with existing IP networks.

– Easy deployment of new services.

– Well understood standards.

The Official Reference Model!

A Simpler Version!

BTS BSC MSC

HLR VLR

OTAF

PDSN AAA

SMS

IP SCP SN

PDN

PSTN

Control of Services

InternetBase Station

Packet data functions

Traditional “Switching Point”

Much More Simpler!

• BTS – Base Transceiver Station

• BSC – Base Station Controller

• MSC – Mobile Switching Center

• PDSN - Packet Data Serving Node

• HA – Home Agent

• IWF – Inter-Working Function

Contents

• Introduction• The 3GPP2 Architecture• Mobility Management in 3GPP2• Functional comparison of 3GPP and

3GPP2.• Architectural comparison of 3GPP and

3GPP2• The MWIF Architecture.

A Mobility Perspective

• Note that, for simple IP, the HA is not used.

• AAA is used for data service authentication.

• The PPP tunnel from the MS terminates at the PSDN which acts as the Foreign Agent (FA).

• The PSDN is the first hop IP router and performs Diffserv shaping, ingress filtering, handoff between PCFs.

• The PDSN is also responsible for forwarding accounting information to the appropriate AAA entity.

• The PCF maintains a layer 2 connection with the PSDN for sending/receiving packets for MSs under its control.

The Ultimate Goal – An All-IP Network

Contents

• Introduction• The 3GPP2 Architecture• Mobility Management in 3GPP2• Functional comparison of 3GPP and

3GPP2.• Architectural comparison of 3GPP and

3GPP2• The MWIF Architecture.

Security and Mobility Management

• 3GPP uses GGSN, SGSN nodes.

• 3GPP does not allow heterogeneous access.

• The HLR is likely to be used by the SGSN for authenticating data users. Thus, access and data network authentication are integrated.

• 3GPP2 uses mobile IP and PSDN as FA/HA .

• It allows heterogeneous access.

• The PDSN uses an AAA infrastructure to authenticate data users. Access and data network authentication are separate.

Services etc.• The 3GPP model has a

SIP-like functionality in the 3 types of Call State Control Functions (CSCF).

• Location service in the 3GPP model is tied closely to the access.

• GTP is used to provide link-layer mobility.

• Though the specification is yet to be published, 3GPP2 has decided to use SIP.

• In the 3GPP2 model, location service is more of a database i.e., access-independent.

• Link layer mobility in the 3GPP2 world is viewed as a direct extension of mobile IP.

Note that,

• Due to the lack of standards for SIP with all potential applications like VoIP, there is a danger of 3GPP and 3GPP2 coming up with incompatible extensions to SIP which would have to be harmonized sometime later.

• The 3GPP2 specification is not as complete as the 3GPP specification.

• In the 3GPP specification, there is an option to place a mobile IP-based Foreign Agent in the GGSN. Still, this would introduce a lot of tunneling overhead in the GGSN-SGSN path (Mobile IP over GTP over IP).

Contents

• Introduction• The 3GPP2 Architecture• Mobility Management in 3GPP2• Functional comparison of 3GPP and

3GPP2.• Architectural comparison of 3GPP and

3GPP2• The MWIF Architecture.

Emergency ServicesNetwork

3G-HLR

UTRAN BSS/GERAN

3G-HLRG-MSC Server

IP Multimedia Subsystem

PS Domain

3G-SGSN 3G-GGSN

R-SGW

MGCF

MGW

PSTN/Legacy/External

T-SGWLegacy mobile

signallingNetwork

MultimediaIP Networks

MultimediaIP Networks

MSC Server

Signaling only User Data and Signaling

BGCF

Applications &Services

SCPCSCF

CSCF

Application

Service

Control

Transport

CS Domain

RAN

3G-HLR

UMS

HSS

MRF

GMLC

MT TE

3GPP All-IP Network Architecture Model

3GPP NAM - Discussion

• 3GPP is divided into 4 planes – IP Multimedia, Packet-Switched, Data-Switched and Radio Access.

• At each plane, there exist data and control functions.

• The picture is very disorganized especially from traditional networking perspective. – Legacy transport gateways are on the same plane as applications.

– HLR and Unified Messaging Service are in limbo.

– As mentioned earlier, the location service is access dependent because of its presence in the lowest layer.

– The CSCF has all the functionality; there is not much modularity.

• Transport and Control reside in the same functional node often.

• Applications have to talk to either of CSCF, HSS, SGSN.

• QoS is implemented in CSCF and GGSN.

Application

Service

Control

Transport Media Gateway Control

Roaming Signaling Gateway

Service Application

Network Capability Gateway

Subscription QoS Manager

Databases

EIR DSI Sub Poli

Trunk Signaling Gateway

MAP41 & GSM

PSTN

IPNetwork

Session Control Manager

Core QoS Manager

Media Gateway

Border Router

Position Server

Position Determining Entity

AAA

Legacy MS Domain Support

Media Resource Function

Mobile IP Home Agent

Access Net.AccessGateway

FA/Attendant

BSC+ PCFBTS

MM

OtherAccess Networks

MS

Signaling-ControlBearerRadio

3GPP2 All-IP Network Architecture Model

3GPP2 NAM - Discussion

• 3GPP2 fits into the Transport, Control, Service, Application Plane model much better.

• The PSDN will have only the HA/FA functionality unlike the GSN nodes.

• Applications talk to only the NCG.

• The modularity of this model over the 3GPP model is seen in the case of the QoS manager.

• The HLR, ESI, location information etc are captured as services available by querying databases.

Contents

• Introduction• The 3GPP2 Architecture• Mobility Management in 3GPP2• Functional comparison of 3GPP and

3GPP2.• Architectural comparison of 3GPP and

3GPP2• The MWIF Architecture.

The Mobile Wireless Internet Forum (MWIF)

• MWIF is a non-profit association of wireless companies whose objective is to define a single mobile wireless and Internet architecture independent of the access technology.

• They have a network reference model to achieve this. Backwards compatibility is still a problem.

• Notice the service discovery server in the MWIF architecture.

• The CSCF functionality is in the CSM and Session Proxy.

Directory Services

i l

Application

Service

Control

Transport

INTERNETIntranet

PSTNMAP

41 & GSM

Enterprise

Home Mobility Manager

Access Network

Terminal UIM

Access Gateway

IP Address Manager

Access Transport Gateway

Mobile Attendant Transport Gateway Functional

Entities

Media Gateway

IP Gateway

Signaling Gateway

Media Gateway Controller

Multimedia Resource Function

Communications Session Manager (CSM)

Session Proxy

Session Anchor

AAA Functional Entities

AuthenticationServer

Home IP Address Manager

AuthorizationServer

AccountingServer

Location Server

Global Name Server

Policy Repository

Profile Server

Application Functional Entities

Core Network Application(s)

3rd Party Application(s)

Multimedia Resource Controller

Resource Manager

Geographic Location Manager

Service Discovery Server

BearerSignaling-Control

Resource Directory

MWIF All-IP Network Architecture Model

Summary• Though the 3GPP and 3GPP2 NAM differ, active

harmonization initiatives such as MWIF are cause for optimism.

• Remember that harmonization on the access is also being tried for (or else dual mode devices would be necessary).

• SIP seems to be the choice for session initiation over H.323 and other protocols.

• There are strong reasons for using IPv6 in 3G networks. But, all commercial 3G networks till date use IPv4 (since it is easier to deploy).