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ping schemes were worked out between UMTS

and GPRS, and between UMTS and GSM.

As the UMTS internal QoS mechanisms became

stable the end-to-end aspects came more into

focus. A policy framework was developed to

support policy rules for the end-to-end commu-

nication on the IP layer. A goal was to make the

interworking with the external networks as

seamless and efficient as possible with high flex-

ibility to convey end-to-end QoS information.

To support QoS related to the IP multimedia

subsystem, SDP (Session Description Protocol)

was used to carry the session parameters. SDP

is a protocol with the SIP family which de-

scribed the resource requirements for the ses-

sion.

When discussing UMTS QoS mechanisms it is

important to bear in mind the strong relationship

between UMTS packet domain QoS and IETF

based QoS mechanisms. It was a goal for 3GPP

to conform as much as possible to IETF based

QoS mechanisms to avoid duplicating work, and

try to provide a smooth and efficient integration/

interworking with external IP based networks.

UMTS therefore adopted DiffServ at the connec-

tivity IP level between RNC and SGSN and

between SGSN and GGSN to support differen-

tiated services. Interworking between UMTS

specific QoS mechanisms and IETF based QoS

mechanisms such as RSVP and DiffServ there-

fore became an important work item. Work is

still on-going in 3GPP around these issues.

In the following we will go into more detail on

the internal QoS provisioning in UMTS. End-to-

end issues are addressed in Chapter 4.

3.2 UMTS Bearers

UMTS specifies different levels of QoS. These

levels are specified with different bearer services

as depicted in Figure 3-2. As shown, the UMTS

system comprises the nodes from the MT to the

CN Gateway. Within this network the QoS will

be ensured by means of different bearer services.

Each bearer service will deploy the services sup-

ported by the layer below. The QoS across the

UMTS network is specified by the UMTS bearer

services comprising the QoS handling in the

UTRAN and in the Core network. The UMTS

bearer services interact with the local bearer ser-

vices on the terminal side and the external bearer

services on the border towards external net-

works. Together these bearer services deliver the

end-to-end service comprising the end-to-end

QoS that the user experiences.

The QoS across the UTRAN is supported by the

RAB (Radio Access Bearer). The RAB is sup-

ported by the Iu bearer service and the Radio

bearer service. The W-CDMA based Radio

bearer comprises the physical wireless transport.

The RAB service may differentiate between ser-

vices classed by deploying different radio chan-

nels, e.g. dedicated channels or shared channels.

Management of the channels regarding e.g. error

control, priority of radio resources etc. varies

between the channel types. Different channel

types may therefore be utilised for different traf-

fic demanding different QoS requirements. Real

time traffic most often deploys dedicated chan-

nels. The Iu bearer service together with the

physical bearer service comprise the services

across the Iub, Iur and Iu interface. An ATM

protocol stack is used across the Iub and Iur

interface as explained in Chapter 2. Across the

Iu interface it is optional to use ATM QoS

mechanisms and/or IP based QoS mechanisms.

If one deploys IP QoS, DiffServ shall be the

mechanisms to support QoS across the Iu inter-

face.

The Core network bearer service for the packet

domain is pretty similar to the Iu bearer service.

At the IP connectivity layer DiffServ handles

service differentiation and QoS support. The

layers beneath the IP level is not specified for

the CN part as it is for the Iu interface.

3.3 QoS Management

To support the required QoS throughout the

UMTS network, and to be able to allocate and

keep track of resource usage internally, each

UMTS entity has to perform certain QoS related

management functions. UMTS specifies man-

agement functions for both the control and user

plane. Figure 2 depicts the QoS management

functions for the control plane.

Figure 3-2 UMTS QoS
bearers

TE MT UTRAN/

GERAN

CN IU

EDGE

NODE

CN

Gateway

TE

External

Bearer Service

CN Bearer

Service

End to end service

Bearer serviceTE/MT Local UMTS Bearer Service

Radio Access

Bearer Service

Iu Bearer

Service

Physical

Bearer

Service

Backbone

Bearer Service

Radio Bearer

Service

Physical

Radio

Service

UMTS