Consultation Paper on Quality of Service (QoS) - ICTA

different for users of interactive applications conversational, messaging or retrieval services and
users of distribution services.
Some measurements (such as fault repair times) are best made by operators. Others are best made
by external measurement agencies, because doing so makes them more comparable between
different operators and, sometimes, less costly 14 .
Quality of Service parameters may be measured either objectively via technical means or
subjectively via surveys amongst the users. Subjective measurement is a time-consuming and
expensive procedure. Therefore, objective measurements are often used where specific network
related QoS parameters measured can be correlated to the user's perception of QoS 15 . However
doing both objective and subjective measurements allows getting the whole QoS picture.
Objective Measurements
Objective measurements are made by measuring physical attributes of circuits, networks and
signals. These measurements can be made either on real traffic or on artificially generated traffic;-
o Intrusive measurement is performed on artificially generated traffic (established test calls)
and the traffic can be tailored to check almost everything.
o Non-intrusive measurement is performed on real traffic conditions and therefore is expected
to give a more realistic vision of the QoS, however not all possibilities are checked.
Subjective Measurements
Subjective measurements are used to assess aspects of QoS that cannot be measured easily by
technical means or that may be missed out due to a limited number of measurement points. They
are used to assess the quality of a service with respect to audio i.e. speech and video quality. This
includes the performance of specific transmission elements. They are also used as reference for
objective measurement methods. Some subjective tests which are described in ITU-T
Recommendation P.800 include: Listening opinion tests, conversation-opinion tests and double-talk
tests, interview and survey tests.
Subjective assessments use surveys of customer opinions to calculate a Mean Opinion Score
(MOS). For instance, Recommendation P.82 recommends the use of telephone user’s surveys in the
manner of Recommendation E.125 (now deleted) as a means of measuring speech transmission
14 ITU document Background <strong>Paper</strong> (Sep. 2006), ICT Quality of Service Regulation: Practices and Proposals- Global
Seminar on Quality of Service and Consumer Protection, Geneva.
15 ITU Handbook (2004), Quality of Service and Network Performance
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