Side_1_360

of the downlink user data traffic with the QoS

attributes of the relevant UMTS bearer ser-

vice. For example, the packet-oriented trans-

port of the downlink data units is received

from the external bearer service and sent

through the core network to the UTRAN and

is buffered at the RNC. If the downlink traffic

results in bursts of data units not conformant

with the UMTS BS QoS attributes, a traffic

conditioner in the UTRAN conforms the data

traffic according to the relevant QoS attributes

as e.g. the peak bandwidth limit.

The traffic conditioner is not necessarily the

only function to ensure that the traffic does not

exceed the QoS attributes. For example a re-

source manager may also provide conformance

with the relevant QoS attributes by appropriate

data unit scheduling. Or, if fixed resources are

dedicated to one bearer service the resource limi-

tations implicitly condition the traffic.

• Mapping:The mapping function (Mapper)
  marks each data unit with the specific QoS
  indication related to the bearer service per-
  forming the transfer of the data unit. This may
  be marking the packets with specific DiffServ
  code points for differentiated treatment in
  DiffServ enabled IP networks.


• Resource manager:Each of the Resource
  Managers of a network entity is responsible
  for a specific resource. The resource manager
  distributes its resource budget between all
  bearer services requesting transfer of data
  units. The resource manager thereby attempts
  to support the QoS attributes required for each
  individual bearer service.

3.4 UMTS QoS Classes

The network must be able to distinguish between

types of services to be able to support different

QoS requirements. Four QoS classes have been

specified:

• Conversational class
  The conversational class supports real-time
  communication between entities. The class
  provides low latency and drop reliability.


• Streaming class
  The streaming class intends to support appli-
  cations which are not real time demanding but
  sensitive to jitter. However, the latency be-
  tween the communication entities must be
  limited within a defined maximum value.


• Interactive class
  The interactive class offers three levels of
  precedence and supports non real-time appli-
  cations.


• Background
  The background class supports non real-time
  demands. The class is served with the lowest
  priorities.

As noted the difference between them is first and

foremost their delay sensitivity, ref. Table 1. The

conversational class is the most delay sensitive.

This class is therefore best suited for real time

services such as voice applications. The back-

ground class is the most delay intolerant class

and is suited for e-mails and file transfer. The

table on the following page gives an overview of

the classes and what types of services are suit-

able to use within each class.

Figure 3-4 QoS management
functions for the UMTS bearer
service in the User plane

Mapper.

MT UTRAN CN EDGE Gateway Ex.

Netw.

Resource

Manager

Resource

Manager

Resource

Manager

Resource

Manager

Resource

Manager

data flow with indication of direction

TE

Class

if.

Cond.

Local BS Resource

Manager

Cond.

ULTRA phys. BS Iu network service

Mapper.

External BS

Mapper.

BB network service

Class

if.

Cond.