teacher guide wcdma/umts - network structure - instructors guide - 3g... · teacher guide...

TEACHER GUIDE

WCDMA/UMTS - NETWORK STRUCTURE

Chapter 2

OBJECTIVES OF CHAPTER 2: Upon completion of this chapter the student will:

• Be familiar with the network convergence concept

• Be familiar with the WCDMA/UMTS architecture

• Retain basic understanding on the operator benefits offered by the Ericsson WCDMA/UMTS network architecture.

WCDMA/UMTS Offerings

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WCDMA/UMTS OFFERINGS

TEACHER GUIDE -

2 NETWORK STRUCTURE

Table of Contents INTRODUCTION ... .......................................................................................................... ...1

CONVERGING PURPOSE-BUILT NETWORKS ... ........................................................ ..2

ERICSSON’S WCDMA/UMTS REFERENCE MODEL ... ............................................... ..5

A PEDAGOGICAL HORIZONTAL NETWORK MODEL FOR AN EARLY PHASE OF THE 2G TO 3G MIGRATION ... ..................................................................... .7

A PEDAGOGICAL MODEL CLOSE TO THE TARGET NETWORK ... .......................... ..8

EXPANSION OF THE TARGET NETWORK TO MANY APPLICATIONS AND MANY ACCESS NETWORKS... ..................................................................................... ..10

INTRODUCTION OF GATEWAY CONTROL PROTOCOLS AND API ... ................... ..11

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2 WCDMA/UMTS - NETWORK STRUCTURE

INTRODUCTION

Tell the students that chapter 2 deals with network structures.

All slides are on an overview level. More details will follow in next chapter (Service implementation overview), showing how the network is used for various services.

Tell the students that this chapter is split into two parts:

• One part similar to ”conventional” presentations of WCDMA/UMTS network structure. In this introductory part of the student text there is focus on the most common target network figures, and their interpretation.

• The other part which uses more pedagogical slides. The reason is that we have found that 3G offers considerable learning hardship

Tell the students that, for pedagogical reasons, there is a strong need for models that represent an early stage of the migration, and also pedagogical models that are close to the target network model, in both cases with clearly visible terminal functions, and some relation to a layered thinking, that has, if possible, relations to OSI.

It is also a need for pedagogical figures treating

• the interface between application and network, and

• the gateway control protocol

• access-core interface

The figure representing the early stage of the migration should also show (roughly) what additional equipment is required compared to the GSM/GPRS structure. (The same figure was included in the guide for chapter 1)

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CONVERGING PURPOSE-BUILT NETWORKS

Today’s Network Solutions PLMN PSTN/ISDN

Services Services

PL PST

MN N/IS DN

Access, Transport Access, Transport

& &

Switching Network Switching Network

IP

Services

Data

/IP

Netw

orks

Access, Transport

&

Switching Network

CATV

Services

CAT

V

Access, Transport

&

Switching Network

Figure 2-1 Today’s network solution. “Vertical” networks.

Tell that the 2G operators operate purpose built networks. They use different nodes and resources (Access, control and transport). For each network solution the operator has KAPEX (Kapital expenses ) and OPEX (Operational expenses). A convergence to one backbone should minimise at least the OPEX.

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2 WCDMA/UMTS - NETWORK STRUCTURE Applications /

Service layer

Control layer

Connectivity

Resource

Node

Appl Servers

SCP HLR SCS

TL/TG MSC GSN

Server Server Server

Connectivity backbone

(ATM, IP, …)

MGW

MGW

H.323/

SIP

Internet MGW Intranets

MGW

PSTN/ISDN/ PLMN

Wireless AN

Wireline AN

(Media) Gateway, handling User Plane

Server, handling Control Plane & Applications

Figure 2-2 Next generation multi-service network

These next-generation packet-ready networks will be organized horizontally in the following layers: (See figure 2.2)

Explain the Layering principles:

• The control layer (seen in the middle of the figure above) is specific to each of the different types of services such as Plain Ordinary Telephony System (POTS), Global System for Mobile Communication (GSM),

General Packet Radio Service (GPRS) and Universal Mobile Telephony System (WCDMA/UMTS). This is where the intelligence for these services will reside - as the name suggests the control layer provides the control for the specific services, for example call control, session control and signalling. Most IN services are network oriented and therefore normally part of this layer.

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• The horizontal structure means that all types of services then use the same transport network - this forms the connectivity layer (user plane) and handles everything that has to do with transport and manipulation of user data. An operator with a multiservice network can then reduce both equipment and operational costs by having this common transport network for all services. For economical reasons it will only be possible to implement this common transport principle in the core, initially.

• And finally, the top layer is the application layer - the applications are as generic as possible in order to enable them to be used for all types of services - these applications would typically be IP applications.

Explain that a common connectivity core is a perfect link between access and service network. For the traffic in the connectivity part a common word is media stream. In order to get a fairly uniform core media stream in a differentiated access network environment there will very often be a need for media conversion at the border between access and core network. This conversion takes place in media gateways (MGW)

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ERICSSON’S WCDMA/UMTS REFERENCE MODEL

Layered UMTS Network Architecture

Services/Application Layer

Application Servers

Management

Applications

SGSN

MSC server server

HLR... GGSN server

Control Layer

IP, GMSC/ IRP Transit server

PSTN/ISDN

Connectivity Layer Internet

MGW MGW Intranets

User data BS

BS

RNC RNC BS Control UTRAN

Figure 2-3 The WCDMA/UMTS reference model

Explain the figure. Do not explain here the node functionality. Use the text book:

In Ericsson’s model the connectivity layer, at the bottom, contains Cello based Media Gateways, and transport backbone elements such as switches or routers. The GSM radio access network and WCDMA radio access network are connected to the backbone network via a Media Gateway. External networks - IP networks and ISDN/PSTN networks - are accessed via other Media Gateways. The User Plane is transported across the backbone network between/via Media Gateways.

In the middle we have the control layer which contains the servers - Here are not only MSC Servers and GSN servers but also HLR Servers, Equipment Identity Register, SCP and so on. The MSC and GSN Servers control the Media Gateways.

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During the migration phase from 2G to 3G (R1 Phase), the main switching centers (MSCs) and SGSN-GGSNs will be logically divided into servers and media gateways. In a pure WCDMA/UMTS network the servers are even physically separated from the Media Gateways (R2 phase). This logical and physical separation ensures maximum flexibility in adapting to changes in traffic patterns and traffic mixes. New transport technologies, for example, can be introduced in one layer without impacting the other layers.

The WCDMA/UMTS server/media gateway architecture provides node redundancy in the event of a media gateway failure or loss of an entire node. It also enables common transport arrangements for multi-services networks, so that several service networks can share the same transport network. And it ensures service portability, i.e. the sharing of a common service layer that is independent of the access network.

The top layer, the Application layer, is where the end user applications reside. The application servers are often complemented with content servers for information retrieval, which host service-related databases or libraries, such as video-clip libraries and news history data bases.

Finally we have the service capability servers, which in principle are network based (control) resources. These resources might control the media stream resources, such as WAP gateways. Many servers are connected to signalling system 7 CAMEL (Customized Applications for Mobile network Enhanced Logic), IN services and MPC (Mobile Positioning Centre). The service capability servers interface with the resources in the Core Network [Here we see that the Control and connectivity layers together form the Resource layer], and with the Application servers, to negotiate the service capabilities needed for a specific application. Examples of other service capability servers are SAT [SIM Application Toolkit], and SMS-C.

Ericsson is also working with developing management applications for this new network architecture.

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A PEDAGOGICAL HORIZONTAL NETWORK MODEL FOR AN EARLY PHASE OF THE 2G TO 3G MIGRATION

(Student text repeated below, since it is descriptive)

The layered 3G network model is not implemented over night. During the migration phase other models may be more useful. Further, from a pedagogical (and business) point of view, the terminals are important for the overall end to end understanding. The services offered to the end users depend largely on the capabilities of the application servers and the terminals/ clients. From a pedagogical OSI model oriented view the client terminals and the application servers are on equal levels (1-7), whereas the network in between is positioned on OSI layers 1-3. This approach gives us a more horizontal network model, where the traffic flows horizontally, as opposed to the WCDMA/UMTS reference model in figure 2-3, with some traffic flowing vertically, from terminals at the bottom to applications at the top.

Another factor is that the migration between two fundamentally different network architectures (circuit mode and IP packet mode) is quite ”painful”. Therefore we have to live with a limited integration for some time. Even though there will be clearly visible circuit and packet networks in the access network and in the core network for some time, it is more stable to use the expressions the “Real time service path” and the “Non-real time services path”. Comparing with the service taxonomy introduced in chapter 1, the real time services belong to the communicative non-asynchronous services.

From start of the migration the circuit mode network part has its intelligence concentrated in the centre of the network. Thus, the migration must embrace an intelligent control layer inherited from the circuit mode. When suitable, this intelligence is also supporting the more straightforward packet mode bearer network in the core. (Billing, security, HLR services, but normally not with IN services.)

Similar to the GSM network, there is a clear separation between the access and the core network. But in WCDMA/UMTS both parts will initially have a circuit mode path and a packet mode path.

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GSM-UMTS Core network IN SCP

Distant

Applications

GSM Radio

Access

GSM BSS

Client

Terminals

WCDMA

Radio Access

UMTS RNS

GSM Specific

UMTS

addition

GSM Specific

UMTS

addition

GMSC

MSC UMTS addition

HLR

UMTS

addition

GGSN

SGSN UMTS addition

PSTN

ISDN

IP Core

Internet

Intranet

Figure 2-4 Pedagogical model. Service network, if any, located to IP Core.

The upper path in figure 2-4 represents a preferable path for real time traffic and initially also multimedia traffic, utilizing circuit mode or ATM AAL2.

The bottom path represents a path for non real time traffic initially, later multimedia traffic over ATM/IP.

This pedagogical model is thus characterized by:

Visible terminals and corresponding application devices at the same level.

Real time and Non real time paths in access and core

Network intelligence in the control layer serving primarily real time/circuit mode but also non real time/packet mode core

A PEDAGOGICAL MODEL CLOSE TO THE TARGET NETWORK

The concept 3G aims at a future network architecture that has

taken advantage of all technological enablers we know of presently.

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Tell the students that you can draw or show a figure as a reference model for that future, which is thus close to a target network.

Draw or show Thomas figure ”NGN target reference model” here

Tell the following about that figure:

”As said in the introduction to this chapter, a layered view is necessary to understand the future network structure.

The key to visualization of layering in the model is to explicitly

include terminal systems as parts of the model.

The separation between network terminations and client machines highlights the separation between connectivity network access with its communication control (and its control servers), and application networks (and its content servers).

The communication relation (2) in the figure represents all kind of end-to-end data application protocols, including WAP, FTP, HTTP, TCP etc.

The communication relation (3) in the figure represents

all kinds of communication control protocol between terminal systems and the network (Q. 931, DTAP, IS 136, UNI, part of Iu, etc.).

The interface (4) and its standardization is a key enabler to isolate access network development from core network service provisioning

There is so far no general name associated to it. In WCDMA/UMTS it is called the Iu- interface. Iu is presently defined to comprise all protocols between access and core networks, and the service control interface (according to (3) between terminal systems and core network.

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Iervice Capability Servers


The gateway control protocol interface (5) (GPC) is a key enabler for implementation of the ”horizontal integration paradigm”.

The application programming interfaces (6) (API) and special service capability servers (as part of the communication control layer) support the integration of application servers to the network”.

EXPANSION OF THE TARGET NETWORK TO MANY APPLICATIONS AND MANY ACCESS NETWORKS

Show fig 2-5.

“WCDMA/UMTS as a whole is often an access network to other networks or to applications outside WCDMA/UMTS. Compare Mobile Internet. For this purpose a horizontally layered view can be used.”

Application 1 Application 2 Application n Open I/F

ntermediate Equipm (SCS)

Other

PLMN

Gen 2 UMTS PLMN Gen 3

members

PSTN/ IMT-2000

ISDN Family

Figure 2-5 WCDMA/UMTS as one of many access networks to

content servers etc. SCSs provide an interface between application and

network resource.

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INTRODUCTION OF GATEWAY CONTROL PROTOCOLS AND API Application 1 Application 2 ………… Application …N

APIs

Service

Capability

Servers

HSS

Packet-Switched

Domain Network Control Layer

Circuit-Switched IP Multimedia Domain Domain

GCP GCP

Figure 2-6 A more generic view of the control layer. The domains in the figure can be seen as “domain resource control” in relation to the resources in the user plane, below

GCP, Gateway Control Protocol

Show figure 2-6 above showing the new important interfaces/protocols API and GCP, enabling a layered network structure.

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