Page 23 - ITU-T Focus Group Digital Financial Services – Consumer Experience and Protection

ITU-T Focus Group Digital Financial Services
Consumer Experience and Protection

with time as people get accustomed to improvements. Therefore, the issue of “typical values” or “threshold
values” is characteristic for the QoE domain.

Objective measurements deal with quantities which can usually be determined by technical measurements,
such as information loss and delay. Subjective elements are components of human perception that may
include emotions, linguistic background, attitude, motivation, etc. which determine the overall acceptability
of the service by the end-user. An important part of subjectivity are expectations which usually are formed by
previous experience of users for the same or similar types of service.

The following figure shows factors contributing to QoE. These factors are organized as those related to Quality
of Service and those that can be classified as human components. QoE for voice and video is often measured
via carefully controlled subjective tests where voice or video samples are played to viewers, who are asked
to rate them on a scale. The ratings assigned to each case are averaged together to yield the mean opinion
score (MOS).

Quality of service (QoS) is defined in Recommendation ITU-T E.800 as the collective effect of performance
which determines the degree of satisfaction of a user of the service. In general, QoS is measured in an objective
way.

In telecommunications, QoS is usually a measure of performance of services delivered by networks QoS
mechanisms include any mechanism that contributes to improvement of the overall performance of the system
and hence to improving the end-user experience. QoS mechanisms can be implemented at different levels.

EXAMPLE: At the network level, QoS mechanisms include traffic management mechanisms such as buffering
and scheduling employed to differentiate between traffic belonging to different applications. Other QoS
mechanisms at levels other than the transport include loss concealment, application Forward Error Correction
(FEC), etc.

QoS parameters are used to describe the QoS observed. Similar to the QoS mechanisms, QoS parameters
can be defined at different layers. Figure 1 below shows the factors that have an influence on QoS and QoE.

Figure 1: Factors that have an influence on QoS and QoE

In general, there is a correlation between the subjective QoE as measured by the MOS and various objective
parameters of Quality of Service.
Typically, there will be multiple service level performance (QoS) metrics that impact overall QoE. The relation
between QoE and service performance (QoS) metrics is typically derived empirically. Having identified the
QoE/QoS relationship, it can be used in two ways:

1) Given a QoS measurement, one could predict the expected QoE for a user.
2) Given a target QoE, one could deduce the net required service layer performance.

These prediction and deduction steps are built on assumptions and approximations.

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