Side_1_360

establishment of the radio access bearer in more

detail.

3.5.1 Overall Procedure

Figure 3-5 shows how the bearer is established

in UMTS. The user establishes a UMTS bearer

(PDP context activation) by specifying the QoS

requested. The SGSN authorises the QoS given

the subscription of the user and does admission

control given its available resources. It then

requests the establishment of a radio access

bearer (RAB). To do so it derives the adequate

QoS profile for the RAB given the QoS profile

of the UMTS bearer. As an example the transfer

delay might be set to 80 ms if the UMTS bearer

QoS profile indicates 100 ms. This mapping is

implementation dependent.

Once the Radio Access Bearer has been set-up

the SGSN forwards the request to the GGSN.

The GGSN will perform admission control and

replies to the SGSN that in turn replies to the

Terminal. Additionally, the SGSN will take the

initiative to configure the Core network bearer.

The QoS proposed by the network may be lower

than that requested by the terminal. The terminal

might reject the establishment of the UMTS

bearer, renegotiate the QoS or accept the QoS.

3.5.2 QoS across IP Transport Networks

The UMTS architecture for the PS domain

deploys IP transport networks for the Iu inter-

face (RNC – SGSN) and for the Gn interface

(SGSN-GGSN). Across these interfaces Diff-

Serv is used as the IP transport layer QoS mech-

anism. Hence, at the RNC, SGSN and GGSN the

QoS mechanisms at the UMTS bearer service

layer are mapped to DiffServ Code Points to pre-

serve the QoS relationship between the protocol

Table 3 Values for the UMTS
bearer service attributes

Figure 3-5 UMTS Bearer
establishment

Traffic Conversational Streaming Interactive Background

class class class class class

Maximum bitrate (kb/s) < 2 048 < 2 048 < 2 048 - < 2 048 -

overhead overhead

Delivery order Yes/No Yes/No Yes/No Yes/No

Maximum SDU size <= 1 500 or 1 502 <= 1 500 or 1 502 <= 1 500 or 1 502 <= 1 500 or 1 502

(octets)

SDU format information

Delivery of erroneous Yes/No/ - Yes/No/ - Yes/No/ - Yes/No/ -

SDUs

SDU 5*10-2, 10-2, 5*10-3, 5*10-2, 10-2, 5*10-3, 4*10-3, 10-5, 4*10-3, 10-5,

Residual BER 10 -3, 10-4, 10-6 10 -3, 10-4, 10-5, 6*10-8 6*10-8

10 -6

SDU error ratio 10 -2, 7*10-3, 10-3,10-1, 10-2, 7*10-3,10-3, 10-4, 10-6 10 -3, 10-4, 10-6

10 -4, 10-5 10 -3, 10-4, 10-5

Transfer delay 100 -> maximum 250 -> maximum

(ms) value FFS value

Guaranteed bit rate (kb/s) < 2 048 < 2 048

Traffic handling priority 1, 2, 3

Allocation/Retention priority 1, 2, 3 1, 2, 3 1, 2, 3 1, 2, 3

QoS Mapping

PDP Cont. Act. (QoS)

RAB set-up (QoS ́)

procedure

Create PDP Cont. Req. (QoS)

Activate PDP Context Accept (QoS) Create PDP Cont. Acc. (QoS)

MS RNC SGSN GGSN

SM SM GTP-c GTP-c

Admission Control