ETSI TS 102 250-1 V2.2.1 (2011-04)

Speech and multimedia Transmission Quality (STQ); QoS aspects for popular services in mobile networks; Part 1: Assessment of Quality of Service

RTS/STQ-00107m

General Information

• Status: Published
• Publication Date: 28-Apr-2011
• Technical Committee: STQ MOBILE - STQ Mobile
• Current Stage: 12 - Completion
• Due Date: 29-Apr-2011
• Completion Date: 29-Apr-2011

Standards Content (Sample)

Technical Specification
Speech and multimedia Transmission Quality (STQ);
QoS aspects for popular services in mobile networks;
Part 1: Assessment of Quality of Service

2 ETSI TS 102 250-1 V2.2.1 (2011-04)

Reference
RTS/STQ-00107m
Keywords
3G, GSM, network, QoS, service, speech
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3 ETSI TS 102 250-1 V2.2.1 (2011-04)
Contents
Intellectual Property Rights . 5
Foreword . 5
Introduction . 6
1 Scope . 8
2 References . 8
2.1 Normative references . 8
2.2 Informative references . 8
3 Abbreviations . 9
4 Guidance on commonly used Terms and Definitions . 9
5 QoS Background . 12
5.1 End-to-End QoS . 13
5.2 Relationship of QoS and Performance . 14
5.3 Relationship of QoS and QoE . 14
5.4 QoS Models in Standardisation Documents . 16
5.4.1 Model of ITU-T Recommendation G.1000 . 16
5.4.1.1 QoS Required by the User (QoSR) . 17
5.4.1.2 QoS Offered by the Service Provider (QoSO) . 17
5.4.1.3 QoS Delivered by the Service Provider (QoSD) . 17
5.4.1.4 QoS Experienced by the User (QoSE) . 18
5.4.2 Model of ITU-T Recommendation E.800 . 18
5.4.3 Phase oriented Aspect Model. 19
6 QoS Assessment Process . 20
6.1 Objective of a QoS Assessment . 20
6.2 Boundary conditions for a QoS Assessment . 21
6.2.1 Setting the Target of the Assessment . 21
6.2.2 Defining the Boundary Conditions . 21
6.2.3 Operational Issues . 21
6.3 Execution of a QoS Assessment . 22
6.4 Validating and Aggregating Results of a QoS Assessment . 22
6.5 Reporting Results of a QoS Assessment . 22
6.6 Matching QoS Results with Targets . 23
6.7 Optimization of QoS Matters . 23
7 Basic Settings for QoS Assessments . 23
7.1 Location where the Measurement is actually performed . 23
7.1.1 Concept of PCOs . 23
7.1.2 Point of Recording (POR) . 24
7.2 Usage of Standardized Units for Data . 24
7.3 Influence of Timeout Values on Failure Ratios . 24
8 Service Independent QoS Criteria . 25
8.1 Unavailability . 25
8.2 Non-Accessibility . 25
8.3 Time Parameters . 25
8.4 Transfer Time . 25
8.5 Content Integrity . 25
9 Service dependent QoS Criteria . 26
9.1 Rate Parameters . 26
9.2 Ratio Parameters . 26
9.3 Service Non-Accessibility . 26
9.4 Setup Time . 26
9.5 Failure Ratio . 26
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4 ETSI TS 102 250-1 V2.2.1 (2011-04)
9.6 Cut-off Ratio . 26
9.7 End-to-end Failure Ratio . 27
9.8 End-to-end Delivery Time . 27
Annex A (informative): Bibliography . 28
History . 29

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5 ETSI TS 102 250-1 V2.2.1 (2011-04)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://webapp.etsi.org/IPR/home.asp).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Specification (TS) has been produced by ETSI Technical Committee Speech and multimedia
Transmission Quality (STQ).
The present document is part 1 of a multi-part deliverable covering the QoS aspects for popular services in mobile
networks, as identified below:
Part 1: "Assessment of Quality of Service";
Part 2: "Definition of Quality of Service parameters and their computation";
Part 3: "Typical procedures for Quality of Service measurement equipment";
Part 4: "Requirements for Quality of Service measurement equipment";
Part 5: "Definition of typical measurement profiles";
Part 6: "Post processing and statistical methods";
Part 7: "Network based Quality of Service measurements".
The present document builds an umbrella document for this multi-part deliverable. It summarizes the basics of Quality
of Service, always seen from the user's perspective. Differences to Quality of Experience (QoE) are also discussed. In
extension to generic definitions, specific definitions for this multi-part deliverable are stated here. Furthermore, it gives
guidance to assure that QoS assessments can be conducted in a meaningful way and proposes an according process.
Part 2 defines QoS parameters and their computation for popular services in mobile networks. The parameter definition
is split into several parts. It contains an abstract definition which gives a generic description of the parameter, an
abstract equation and the corresponding user and technical trigger points.
The harmonized definitions given in part 2 are considered as prerequisites for the comparison of QoS measurements and
measurement results.
Part 3 describes the measurement procedures needed to perform the measurements of QoS parameters in line with the
definitions given in part 2, applying the test profiles defined in part 5.
Part 4 defines the minimum requirements of QoS measurement equipment for mobile networks in the way that the
values and trigger points needed to compute the QoS parameter as defined in part 2 can be measured following the
procedures defined in part 3. Test equipment fulfilling the specified minimum requirements will allow performing the
proposed measurements in a reliable and reproducible way.
Part 5 specifies typical measurement profiles which are required to enable benchmarking of different mobile networks
both within and outside national boundaries.
Part 6 describes procedures to be used for statistical calculations in the field of QoS measurement of mobile networks
using probing systems.
Part 7 describes how Quality of Service measurements should be done inside the network without direct access to the
end point terminal.
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6 ETSI TS 102 250-1 V2.2.1 (2011-04)
Introduction
The term Quality of Service (QoS) is extensively used today, not just in the telecommunication world in which it has its
roots, but increasingly regarding broadband, wireless and multimedia services that are based on the IP protocol.
Networks and systems are gradually being designed in consideration of the end-to-end performance required by user
applications; however, the term QoS is usually not well-defined, is used loosely or, worst of all, misused. Therefore,
guidance is needed on how to understand and apply the term QoS.
The term "Quality of Service" addresses technical as well as non-technical aspects affecting a service. Different
concepts and guidance have been developed to cover various interests and viewpoints of all parties of
telecommunications service market, i.e. users, service providers, network operators, manufacturers and regulators.
In many cases, the user and his or her expectations with respect to quality are in the centre of interest. This very generic
topic can have manifold characteristics:
• Depending on the role of the user, his expectations may vary: Considering service quality he might have other
expectations compared with situations that are oriented more commercially, e.g. when he is in contractual
discussions with his service provider.
• Not only service usage is relevant to the user. The overall impression of all touch points with his provider is
influencing his personal quality reception.
• Furthermore, the user compares his expectations with the reached level of fulfilment. Future decisions will be
based on his personal perception of the achieved level of quality. In this case, subjective components get an
increased weight and importance. Taking these aspects also into account, the term "Quality of Service" has to
be extended to "Quality of Experience" with a more subjective meaning.
This multi-part deliverable covers all facets which are relevant to the assessment of Quality of Service as seen from a
user's perspective but with a technical interpretation. Whereas the "user's perspective" reflects events and triggers
observable by a user, the "technical interpretation" is related to the fact that quality statements should be reproducible,
comparable and reliable. Often automation techniques are used to achieve these goals based on a statistically valid data
basis.
From a more practical view, different assessment methods are discussed. In a further step, the preparation and execution
of assessment procedures are shown as well as the generation of key performance indicators, their aggregation and their
matching against pre-defined target values. Finally, consecutive steps like optimization procedures are concluding this
process-like view of QoS.
Also belonging to the more practical clause of the present document, basic definitions of measures are provided. To
generate a common understanding of service independent and service dependent measures is also a goal which the last
clauses of the present document should achieve.
In detail, the present document describes Quality of Service from a more theoretical and a more practical view.
Clauses 4 and 5 build the theoretical background of all Quality of Service related matters:
• Clause 4 reflects all relevant definitions and abbreviations which are used in terms of Quality of Service. They
are compiled from different sources like reference documents, involved services and standardization
discussions.
• Clause 5 contains background information to Quality of Service. This rather theoretical clause discusses
generic definitions of Quality of Service, Performance and Quality of Experience. Furthermore, QoS models
defined in further standard documents and their interrelations are a subject of discussion.
Clauses 6 to 9 lead step by step from theoretical discussions on QoS to issues which are of practical and pragmatically
relevance:
• Clause 6 presents a sequential order which describes a QoS assessment as being a process. Starting with the
definition of targets and required preparation steps, the execution of the assessment as well as validation,
reporting and optimization matters are discussed.
• Clause 7 provides basic definitions which are required to have a common understanding on fundamental
topics. Examples are question like "What is a kilobyte?" or "How to define a timeout value?".
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7 ETSI TS 102 250-1 V2.2.1 (2011-04)
• Clause 8 deals with service independent QoS criteria, namely QoS parameters which are of relevance before a
service is used. This covers e.g. the connection dialup via mobile networks.
• Clause 9 handles service dependent QoS criteria. Depending on the service, different parameters are required
or not to give a complete picture of this service's QoS.
The standardization work in the QoS area is still ongoing. Therefore, the definitions and procedures given in will have
to be reviewed on a regular basis to keep them up to date. The information contained in the present document will form
among other input the basis for further work, but is likely to be modified and amended. Therefore, it is recommended to
cross-check the given information with actual discussions within ITU-T and ETSI and with standards published after
the date of publication of the present document.
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8 ETSI TS 102 250-1 V2.2.1 (2011-04)
1 Scope
The present document serves as a generic umbrella document for the further documents part 2 to part 7 of this series. It
gives an overview over the topics addressed by these documents and enables the reader to work with the documents in
the intended way. It is important to understand that the complete series of documents focuses on Quality of Service
which stands for the objective discussion of quality measures from a rather technical perspective. Based on existing
quality standards and further definitions, a complete picture of Quality of Service as seen from a user's point of view is
drawn.
Wherever possible, existing ITU-T or ETSI definitions are referenced. If ITU-T or ETSI definitions do not exist or are
considered as too generic, a more service and mobile network specific definition is made.
The present document comprises the theoretical backgrounds to understand terms like "Quality of Service", "Network
Performance" and "Quality of Experience". Their meaning and interrelation are discussed by taking different QoS
models into account.
2 References
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
reference document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee
their long term validity.
2.1 Normative references
The following referenced documents are necessary for the application of the present document.
[1] ITU-T Recommendation E.800: "Definitions of terms related to quality of service".
[2] ITU-T Recommendation G.1000: "Communications Quality of Service: A framework and
definitions".
[3] ETSI TS 102 250-7:" Speech and multimedia Transmission Quality (STQ); QoS aspects for
popular services in GSM and 3G networks; Part 7: Network based Quality of Service
measurements".
2.2 Informative references
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] ITU-T Recommendation I.350: "General aspects of quality of service and network performance in
digital networks, including ISDNs".
[i.2] ITU-T Recommendation P.10/G.100: "Vocabulary for Performance and QoS".
[i.3] ITU-R Recommendation BT.500-11: "Méthodologie d'évaluation subjective de la qualité des
images de télévision".
[i.4] ITU-T Recommendation X.745: "Information technology – Open Systems Interconnection –
Systems Management: Test management function".
[i.5] ITU-T Recommendation G.109: "Definition of categories of speech transmission quality".
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9 ETSI TS 102 250-1 V2.2.1 (2011-04)
[i.6] ITU-R Recommendation P.800: "Methods for subjective determination of transmission quality".
[i.7] ITU-T Recommendation E.802: "Framework and methodologies for the determination and
application of QoS parameters ".
[i.8] ETSI TR 102 493 (V1.2.1): " Speech and multimedia Transmission Quality (STQ); Guidelines for
the use of Video Quality Algorithms for Mobile Applications".
3 Abbreviations
For the purposes of the present document, the following abbreviations apply:
FEC Forward Error Correction
FTP File Transfer Protocol
IP Internet Protocol
MAC Medium Access Control
MO Mobile Originating
MOS Mean Opinion Score
NP Network Performance
PCO Point of Control and Observation
POR Point Of Recording
PTN Network Termination Point (PTN)
QoE Quality of Experience
QoS Quality of Service
QoSD Quality of Service Delivered
QoSE Quality of Service Experienced
QoSO Quality of Service Offered
QoSR Quality of Service Required
RLC Radio Link Control
RNC Radio Network Controller
RRC Radio Resource Control
SLA Service Level Agreement
SQL Structured Query Language
UNI User Network Interface
4 Guidance on commonly used Terms and Definitions
Throughout this multi-part deliverable, the following terms and definitions apply:
NOTE 1: Several terms and definitions presented in this clause are defined in ITU-T Recommendation E.800 [1],
ITU-T Recommendation E.802 [i.7] and G.1000 [2].
• 1 kByte: 1 024 Byte.
• 1 MByte: 1 024 kByte.
• Access Point Name: Is used to identify a specific IP network and a point of interconnection to that network.
• Active Testing: Refers to the way that data is acquired actively for the measurement, i.e. that the test makes
use of a dedicated channel for the measurement, e.g. by dialling a number and making a call, i.e. setting-up a
channel for the measurement.
• A-party: Initiating part of a connection (also: Mobile Originating, MO) OR in direct transactions, the party
initiating the transaction (calling party).
NOTE 2: In store-and-forward transactions, the party sending content.
• Benchmark: Evaluation of performance value/s of a parameter or set of parameters for the purpose of
establishing value/s as the norm against which future performance achievements may be compared or
assessed.
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• B-Party: In direct transactions, the termination or counterpart of a transaction.
NOTE 3: In store-and-forward transactions, the party receiving content.
• Broadcast: Information transfer from one transmitting entity to many receiving entities.
• Content: Entirety of information transferred within a transaction, seen from the user's perspective.
NOTE 4: In case of services requiring entrance procedures (e.g. server login with FTP), information flow to
achieve the state of being able to transfer actual user data is not counted as content.
• Cut-off: Unintended termination of a communication session.
• Data Service: Telecommunications service involving the transport of data via the PTN such that any user can
use equipment connected to a network termination point to exchange data with another user of equipment
connected to another termination point.
• Direct Service: Service which makes use of direct communications between a client entity and a server entity
without persistent storage of transferred data in interconnected network elements.
• Download: Transfer of data or programs from a server or host computer to one's own computer or device.
• Drive test tool: end-point test tool which is designed to be moved around, i.e. by walking or driving a car.
• Email: Messages automatically passed from one computer user to another, often through computer networks
and/or via modems over telephone lines.
• End-to-end Quality: Quality related to the performance of a communication system, including all terminal
equipment. For voice services it is equivalent to mouth-to-ear quality.
• Event: In this multi-part deliverable, an event is understood as a change of condition (the according point of
time is considered in addition).
• Host: An entity that provides client stations with access to files and printers as shared resources to a computer
network.
• Idle Mode: A communication device is in this state when it is powered-on but not transmitting a signal
Intrusive Testing: According to the definitions ITU-T Recommendation X.745 [i.4], clause 3.10.3, intrusive
test means: "A statement made with respect to a test invocation if service/user disruption will or may occur as
a result of the test". This refers to the way that data is acquired for the measurement, i.e. whether or not
sending a specific predefined and known reference signal over a channel for analysis purposes is required.
NOTE 5: In contrast to active testing, intrusive testing means that a test signal is sent over the network.
NOTE 6: The combinations "active and intrusive testing" and "passive and non-intrusive testing" define the most
common test situations.
• IP Service Access: Basic access to the generic packet-data transfer capabilities the service is based upon.
• Landing Page: The first website that appears in the Internet browser when a user tries to browse the Internet. It
is often used to allow the user to make some specific settings for the following Internet session.
• Maximum Expected Delivery Time: For store-and-forward services, this defines the time span within which a
message shall be received by the B-party to rate the transaction successful from the user's perspective.
• Mean Data Rate: Average data rate of a data transmission, calculated by dividing the number of transmitted
bits by the duration of the transmission.
• Mean Value: In this multi-part deliverable, the mean value is understood as the estimated expectation value of
a distribution. See also arithmetic mean definition from statistics or part 6 of this series.
• Network Access: Access to the network under test.
• Network Accessibility: The probability that the user of a service after a request (to a network) receives the
proceed-to-select signal within specified conditions.
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11 ETSI TS 102 250-1 V2.2.1 (2011-04)
• Network Availability: Probability of success of network functions performed by a network over a specified
time interval.
• Network Operator: Organization that provides a network for the provision of a public telecommunication
service.
• Non-intrusive Testing: According to the definitions in clause 3.10.5, non-intrusive test means: "A statement
made with respect to a test invocation if no service/user disruption will or may occur as a result of the test".
This refers to the way that data is acquired for the measurement, i.e. whether or not sending a specific
predefined and known reference signal over a channel for analysis purposes is required.
• Passive Testing: Refers to the way that data is acquired passively for the measurement, i.e. that the test makes
use of an existing channel for the measurement, e.g. by tapping a further defined point of this channel.
• Probing Attempt: Trial to examine if the service under test works as expected.
• QoS Criterion: Single characteristic of a product or service that is observable and/or measurable.
• QoS Indicator: A characteristic that is used to determine the Quality of Service.
• Quality: The totality of characteristics of an entity that bear on its ability to satisfy stated and implied needs.
NOTE 7: The characteristics should be observable and/or measurable. When the characteristics are defined they
become parameters and are expressed by metrics.
• Rate: Change of amount of a quantity divided by the portion of time during which it has been changed.
NOTE 8: The denominator's unit is related to time.
• Ratio: measurement result which represents a subgroup of all single measurements is related to the total
number of executed single measurements.
NOTE 9: Usually, nominator and denominator share the same unit, namely a counter for measurements
(subgroup/all).
• Reliability: The probability that an item can perform a required function under stated conditions for a given
time interval.
• Retrieval: Transport of content from network to B-party, initiated by the B-party.
• Service: A set of functions offered to a user by an organisation constitutes a service.
• Service Access: A set of functions offered to a user by an organisation constitutes a service.
• Service Integrity: The degree to which a service is provided without excessive impairments, once obtained.
• Service Retainability: Service retainability describes the termination of services (in accordance with or against
the will of the user).
• Session: Continuous usage of a given service, e.g. a speech call or a data session.
• Session Time: Duration of a session.
• Setup: The period starting when the address information required for setting up a call is received by the
network (recognized on the calling user's access line) and finishing when the called party busy tone, or ringing
tone or answer signal is received by the calling party (i.e. recognized on the calling user's access line). Local,
national and service calls should be included, but calls to Other Licensed Operators should not, as a given
operator cannot control the QoS delivered by another network.
• Speech Quality: Quality of spoken language as perceived when acoustically displayed. Result of a perception
and assessment process, in which the assessing subject establishes a relationship between the perceived
characteristics, i.e. the auditory event, and the desired or expected characteristics.
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12 ETSI TS 102 250-1 V2.2.1 (2011-04)
• Speech Transmission Quality: Speech quality related to the performance of a communication system, in
general terms. Categories of speech transmission quality are defined in ITU-T Recommendation G.109 [i.5],
based on the prediction of the E‑model, i.e. in terms of ranges for the transmission rating factor R.
• Store and Forward: Store-and-forward services are services where content is stored in the network and
delivered to the recipient to a later point in time.
• Streaming: Multimedia data (usually combinations of voice, text, video and audio) transferred in a stream of
packets that are interpreted and rendered, by a software application as the packets arrive.
• Talk Burst: Flow of media, e.g. some seconds of speech, from a terminal while that has the permission to send
media.
• Test case: Consists of a number of single identical transactions.
• Timeout: Specified period of time that will be allowed to elapse in a system (e.g. inactivity) before a specified
event is to take place.
• Transaction: Single, complete, typical usage of a particular service.
• Trigger: Always defined with respect to a particular transaction - An event adopting one of the trigger roles for
a particular transaction.
• Trigger Event: See "Trigger".
• Trigger Point: Absolute time (a.k.a. "point in time") of occurrence of a trigger event. Note, however, that this
term is widely used in a less restrictive manner, meaning either the event or its time of occurrence,
respectively, depending on the context.
• A specific event adopting one of the trigger roles for a particular transaction is often referred to as "technical
trigger point" (for this transaction). It occurs / is measured at a specific PCO.
• User Equipment: Technical device in user's possession, used for communication purposes.
• Video: A signal that contains timing/synchronization information as well as luminance (intensity) and
chrominance (colour) information that when displayed on an appropriate device gives a visual representation
of the original image sequence.
5 QoS Background
ITU-T Recommendation E.800 [1] provides the basic definition of QoS and highlights operational aspects of providing
networks and services. In doing so, ITU-T Recommendation E.800 [1] already gives a QoS definition and a framework
for QoS implementation.
The definition given in ITU-T Recommendation E.800 [1] is as follows:
Totality of characteristics of a telecommunications service that bear on its ability
to satisfy stated and implied needs of the user of the service.
Thus, in general QoS is focused on the service from the user's viewpoint being a complete end-to-end view. However,
since the QoS consists of the collective effect of numerous single performances, any QoS analysis will have to deal also
with sub-parts, e.g. network and terminal performance that can be analyzed separately and independently from another.
Therefore, there are a lot of standards and concepts dealing with QoS that are focusing on specific details and aspects of
QoS.
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The perceived quality of a service is the result of the combined influence of the performance of networks and terminals
as well as the perception and expectation of the user. Thus QoS should also take into account both the user's and the
service provider's point of view; it should always be judged from these different perspectives. There is an interrelation
between user's requirements and his perception of the delivered quality on the one hand and the service/QoS planned
and achieved by the service provider on the other hand.
A comprehensive view on QoS should take into account all aspects and perspectives including the numerous standards
dealing with specific sub-parts of QoS. In the following clauses basic issues that need to be considered are discussed in
more detail.
5.1 End-to-End QoS
As already indicated QoS covers the whole end-to-end view of a telecommunications service and can be subdivided in
separate parts that all have an influence on the resulting QoS. The degree of QoS depends on the collective effect of all
sub-parts. This is illustrated in Figure 5.1.
The Figure 5.1 is inspired by ITU-T Recommendation E.800 [1].

User User Access Core Access User User
Equipment Network Network Network Equipment
Network Network Network
Performance Performance Performance
Overall Network Performance
(from UNI to UNI)
End-to-end Quality of Service (QoS)
Quality of Experience (QoE)
Figure 5.1: End-to-end QoS
Quality measures in telecommunications can be determined in a hierarchical manner:

• Network Performance (NP): The network performance is assessed across a part of a network or a
sub-network. Mostly, the NP is given in a technical way by assessing technical parameters which describe the
performance of this part of the network in the desired way. Examples are parameters like bit error ratio,
sending and receiving power, transmission delay, etc.
• Overall NP: If several network sections should be considered as being one integral part of the network
("black box"), the overall network performance has to be assessed. For example, the network performance of
the complete network transmission between the two User Network Interfaces (UNI) can be summarized in this
way.
• End-to-end Quality of Service (QoS): The assessment of the overall transmission chain from a user's
perspective is considered to deliver the Quality of Service in an objective manner. This implies that the most
complete transmission chain without involving the user himself should be taken into account. Mostly, the
generated measures rely on service related characteristics without knowing any details about the underlying
network sections which are required to have an end-to-end service at all.
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14 ETSI TS 102 250-1 V2.2.1 (2011-04)
• Quality of Experience (QoE): The inclusion of the user himself to the overall quality in telecommunications
extends the rather objective Quality of Service to the highly subjective Quality of Experience. The QoE differs
from user to user since it is influenced by personal experiences and expectations of the individual user.
5.2 Relationship of QoS and Performance
It is important to understand that QoS differs from network and terminal performance. QoS is the outcome of the user's
experience/perception, while the network and terminal performance is determined by the performances of network
elements one-by-one, or by the performance of the network as a whole including the performance of the attached
terminals, i.e. the combination of the performance of all single elements. This means that the network performance may
be used with an end-to-end meaning, but it may also be used to describe the performance of a network section.
EXAMPLE: Access performance is usually separated from the core network performance in the operations of a
single IP network, while Internet performance often reflects the combined NP of several
autonomous networks.
However, the network and terminal performance have an influence on the QoS; they represent a part of it. The
combined effect of the performance of all elements determines the overall service performance. There are intrinsic
relationships between QoS and performance parameters, the former having a direct or indirect, and sometimes even
inverse, influence on the latter. Furthermore, some performance measures can have a direct QoS meaning, while some
others have to be combined in order to have a QoS signification.
Performance parameters are used to measure objectively the performance of specific network and terminal elements that
have an influence on the resulting end-to-end quality of a service. Performance is measured and expressed in
performance parameters. The main difference between QoS and network performance is that QoS provides quality
information on an end-to-end and service related basis, whereas network performance specifies the technical
operativeness of network and terminal elements or of network sections.
ITU-T Recommendation I.350 [i.1] provides the following conceptual categorization of Quality of Service (QoS) and
Network Performance (NP) metrics as follows:
Quality of Service parameter Network Performance parameter
User oriented Network provider oriented
Service related attributes Network element and technology related attributes
Focus on user observable effects Focus on planning development (design), operations and
maintenance
Observed at service access points for the users, Observed at network connection element boundaries, e.g.
independent of network process and events relating to protocol specific interface signals

5.3 Relationship of QoS and QoE
In addition to the term QoS, the term Quality of Experience (QoE) is often used nowadays in order to stress the purely
subjective nature of quality assessments in telecommunications and its focus on the user's perspective of the overall
value of the service provided.
The increased significance of the term QoE is related to the fact that in the past the term QoS was used laxly and mostly
for only technical concepts focused on networks and networks elements. The definition of QoS, however, does include
the degree of satisfaction of a user with a service. Thus, non-technical aspects are included, like e.g. the user's
environment, his expectations, the nature of the content and its importance. But most service providers did use the QoS
only in relation to the actual user-service interaction in order to cross-check whether the user requirements have been
met by the service implementation of a provider (as perceived by the user). So there was a strong focus on the actual
network performance and its immediate influence on user perceivable aspects while additional subjective and not
directly service related aspects were omitted.
QoE is defined in ITU-T Recommendation P.10/G.100 [i.2] in Appendix I as the overall acceptability of an application
or service, as perceived subjectively by the end-user. It includes the complete end-to-end system effects (client,
terminal, network, services infrastructure, etc) and may be influenced by user expectations and context. Hence the QoE
is measured subjectively by the end-user and may differ from one user to the other. However, it is often estimated using
objective measurements.
ETSI
15 ETSI TS 102 250-1 V2.2.1 (2011-04)
Contributing to the QoE are objective service performance measures such as information loss and delay. Those
objective measures together with human components that may include emotions, linguistic background, attitude,
motivation, etc. determine the overall acceptability of the service by the end-user. Figure 5.2 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 video is often measured via carefully controlled subjective tests (ITU-R Recommendation BT.500-11 [i.3] and
ITU-R Recommendation P.800 [i.6]) where video samples are played to viewers, who are asked to rate them on a scale.
The rating assigned to each case are averaged together to yield the mean opinion score (MOS).
Quality of service (QoS) is defined in ITU-T Recommendation E.800 [1] 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 servic
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