Telecommunication Service and Experience Quality
Sigit Haryadi Institut Teknologi Bandung
Lantip Safari Media – 2013 – 1st Edition
2
Telecommunications Service and Experience Quality Copyright © 2013, Lantip Safari Media. ISBN :
978-602-18578-6-1
All rights reserved, No portion of this publication may be copied, reproduced, stored in a retrieval system, or transmitted in any form by any means, mechanical, electronic, photocopying, recording or otherwise, without written permission from the publisher. Dago Press is registered trademarks of CV Lantip Safari Media, Inc. Anggrek Residence B4, Ujung berung Bandung, West Java, Indonesia 40294. Email:
[email protected]
Website: www.dagopress.com 3
Thanks Note To whom I would like to thank. I could not possibly list all, but I never forgot all the people who means something to me, even if that people are consider me nuts. Firstly thanks to God. Thank you to all of my family members. Thank you for my wife Westi Riani, my son Salman
Aditya
Firaas
and
my
daughter
Salma
Huda
California. Thank you to all colleges in Bandung Institute of Technology (ITB). Thanks to all of my students.
4
Preface I wrote this book, based on my experience of teaching at university
and
become
experts
in
telecommunication
providers and regulators for over 28 years. This book shows you how to maintain the quality of telecommunications services, which in order to achieve the goal, we need to understand a few things coherently. 1. Know the basic theory of QoS (Quality of Service) and QoE (Quality of Experience). 2. Know the procedure of the Key Performance Indicator Determination.
5
3. Know
the
theory
and
practice
of
performance
measurement. 4. Know the process of telecommunication services and their relation to Signaling Ladder Diagram. 5. If we understand the four steps above, then we will acquire all possibilities of disruption to the quality of the
service,
experiences,
and so
we
the can
quality
of
anticipate
the
customer
precisely
and
quickly. Five steps above would be perfect, if done with reference to the reference to the international telecommunications standards. In addition, we also need to study the practices undertaken by many
6
telecom operators in the world and the regulations issued by several national telecommunications regulator.
January 2013 Sigit Haryadi - Associate Professor at- Bandung Institute of Technology (ITB) - Bandung - Indonesia
7
INTRODUCTION QoS (Quality of Service) and QoE (Quality of Experience) are the
two
most
important
terms
of
telecommunications
services, both QoS and QoE is perfect, can only be said to be really successful. This book shows you how to maintain the quality of telecommunications services, which in order to achieve the goal, we need to understand a few things coherently: In order to understand the process of service established and terminated, we need to understand a few things coherently.
8
First, the quality parameters that are used as a key indicator of the performance of each service. Quality of service is determined by the achievement of some performance indicators. ITU-T and other international standardization
bodies
have
set
outline
Indicator
performance that must be met by each type of service. In
practice,
any
provider
that
provides
telecommunications services, choose some to be a key performance
indicator,
referred
to
as
KPI
(Key
Performance Indicator). In general, there are two groups of KPIs, which are related to the quality of the network and related to the quality of each service. ITU-T Service support performance. ITU-T split into 9
four groups of QoS: Service operability performance, Severability
performance
and
Service
security
performance. Each KPI has a few parameters. In this book described the ways to determine KPI and KPI examples.
Second, the beginning of the development process of service until the service was over, which refers to the SLD (Signaling Ladder Diagram) of each service. Not at all know the quality of telecom services, without knowing that a service set up by SLD. SLD
is a
sequence of signal delivery both the forward and the backward direction, link by link or end-to-end from the
10
beginning to the end of the establishment of a service provider to its customers
Third,
the
relationship
between
key
performance
indicators and SLD (Signaling Ladder Diagram). Once you know what the parameters are set to KPI and SLD of each service, then we have to study the relationship between key performance indicators and SLD. This step is very important, because it will cause us to be a signal are involved in the process of a service.
Fourth, analysis of potential interference and its relation to SLD (Signaling Ladder Diagram). Finally, in order
to
be
able
to
maintain
the
quality
of
telecommunication services, then we need to know 11
what the potential interference that might occur. Each customer has its own assessment of the service they experienced,
and
each
provider
also
has
a
KPI
measurement results. Each occurred KPI measurement results are less good, it must find the cause, and this is easiest if we start from the SLD (Signaling Ladder Diagram) of each service. The basic theory of QoS (Quality of Service) and QoE (Quality of Experience). One key to the success of maintaining both QoS and QoE is to understand the SLD (Signaling Ladder Diagram) of each service. Here is an example of the SLD, studied here so that we
would
understand
more
about
the
process
of
telecommunication services. Let me break it down in the 12
form of question and answer, this refers to the experience as a teacher for over 28 years, which I find to be more intelligent, as having critical students, who are willing and able to ask intelligent questions. Also please be understood, in this SLD below, is not clear which network elements in the network will process and answer the signal. In chapter 5, 6 and 7, are shown SLDs which are more fitting to the industry reality. SLD in this example is simplified to provide an overview only. Analyze from the example of Telephony Signaling Service Ladder Diagram in fig. 1:
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a. What signals sent by the UE (User Equipment) to the network, when the user presses the "SEND BUTTON" b. What happens if the logical channel that prepares the traffic channel in the network can not be formed? c. What happens if the user, for some reason, included in the black list of the provider? d. What happens if the B-party busy? e. Give a formula of the SCR (Successful Call Ratio) and non-Accessibility Telephony Service. f. Describe the ugliness on the SLD that is in this problem?
14
15
Answer: a. Signals sent by the UE (User Equipment) to the network, when the user presses the “SEND BUTTON” are a “Channel Request” NOT a “Service Request”. People who have never know SLD (Signaling Ladder Diagram) of the telephony service, would have thought that when A-party pressing the SEND button, the user equipment will send a "Service Request". b. If the logical channel that prepares the traffic channel in the network cannot be formed, the network does not send a signal "Immediate Assignment", the A-party will wait until the logical channel is ready, and the network
16
will send an "Immediate Assignment", then the A-party will send a "Service Request". c. If the user, for some reason, included in the black list of the provider, the authentication process will not be successful, the network will not send "Ciphering Command". Otherwise, when the user successfully passes the authentication, but the SIM card has a problem, a "Ciphering Command" was sent by the network, and user equipment will respond by sending "Ciphering Complete" and "setup", but network will not answer a "Call Confirmed". d. If the B-party busy, the network does not send a signal "Alert", it will send a "B-party Busy". 17
e. SCR formula = number of “alert” signals divided by the number of "Channel Request". It should be noted that the definition of success is the success of network telephone service to prepare a connection between Aparty
and
B-party,
NOT
considered
when
the
conversations had taken place. If a successful-call setup has occurred, the network sent an “alert” to the A-party and sends the "Ringing" to the B-party. If the B-party answers: the network will send a signal "connect" to the A-party, and A-party answered with a "Connect Acknowledge", and the conversation begins. f. Ugliness in the SLD in this problem, is not elaborate the network into network elements. For example, while 18
the user equipment sends a "channel-request", it is not clear
which
network
elements
are
received.
For
example, in the mobile networks SLD, each incoming signal to the network, it must be accepted first by the BTS or Node-B, but it certainly will be passed to a higher hierarchy of network elements. This “higher” network element will process the
"channel-request"
signal and will answer, by sending an "Immediateassignment" signal to the user.
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Chapter 1: QoS and QoE Theory In this chapter, I will describe the theories of QoS and QoE, please allow me to write a summary of the theory contained in
several
telecommunication
books
and
international
standards Telecommunication Services Topology [1] The telecommunication network is formed by elements of the network.
Network
elements
are
connected
through
a
network topology. Each network topologies and network elements formed specifically to serve one or several types of telecommunications services.
20
Topology of the most conventional services
for
public
use
is
telecommunications
PSTN
(Public
Switch
Telecommunication Network). At first it can only provide PSTN phone service, and with a few modifications to the local-loop, PSTN
is used to
deliver
conventional
data
communication services, namely telegraphy. . PSTN still exist today, after a lot of evolution, yet still provides two basic services comprising telephone and internet. Further developing of the network topology to serve mobile communication is PLMN (Public Land Mobile Network Mobile). At
first,
PLMN
only
can
serve
telephone,
called
1st
Generation, commonly abbreviated as 1G. Later, other than
21
just to serve the phone, PLMN are also able to serve the internet with a few tens of kbps maximum speed, 2G, which quickly evolved into a 3G, which can reach a maximum speed of internet several Mbps. It took a relatively long time, and then evolves to 4G, which the telecommunications network and the services it could provide, all based on IP. Network topology describes the network elements and links between
network
elements,
through
which
telecommunication traffic on a certain telecommunication service, end to end. Topology depends on two things:
The types of Service 22
The types of Technology.
For example, the network topology of the PSTN (Public Switch Telecommunication Network) is different than the PLMN (Public Land Mobile Network). Two PLMN both to serving telephone, GSM topology is different than CDMA. Two GSM, both serving telephone, network topology of 2 G and 3G are different. A GSM 3 G, which serves a phone call and the other GSM 3G serves the SMS will have a different topology.
23
Types of telecommunications services [1] There
are
many
ways
to
classify
the
types
of
telecommunications services. For example, here are 3 ways to group, which is based on the ITU-T, ETSI and GSMA. Grouping telecommunications services according to ETSI standards TS.102.250 series [2]:
Direct services. That includes direct services are: o Telephony o HTTP (web browsing) o Streaming o FTP o Ping 24
o mobile broadcast o Push to talk o Video telephony.
Store and forward service. That includes store and forward services are: o E-Mail o SMS (Short Message Service) o MMS (Multimedia Message Service).
In the ITU-T G.1010 series, telecommunication services are grouped into [3]:
Audio services. That includes audio services are: o Conversation voice
25
o Voice messaging o High quality streaming audio
Video services. That includes video services are: o Videophone o One-way video
Data services. That includes data services are: o Web browsing HTML o Bulk data transfer / retrieval o Transaction service-high quality for a variety of purposes, such as ATM,
e-commerce,
command/control services, Interactive games, Telnet, E-mail server access, E-mail server to
26
server transfer, real time fax, store & forward fax, Low priority transaction and UseNet. According
to
the
GSMA
standard
PRD
IR
42,
telecommunication services consisting of [4]:
Telephony
SMS
Circuit Switched Data Service
Packet Switched Data Service
Conversational data Class
Streaming Class, Interactive Class
Background Class.
27
Definition of the QoS (Quality of Service) Quality of Service (QoS) consists of a set of parameters related to the performance of traffic on telecommunication network. QoS definitions contained in the ITU-T as: “The collective effect of service performance which determine the degree of service user satisfaction” [5]. In addition to the above definition, there are several other QoS concepts:
Service support performance
Service operability performance
Severability performance and
Service security performance 28
Complete definition contained in the ITU-T E.800 series. Telecommunication operators and service providers are able to provide better QoS, are more likely to retain existing customers and may increase again from rival operator customer churn. But a better QoS requires greater costs. Normally, each operator will balance QoS and cost.
Multimedia Quality of Service [2] ITU-T
Recommendation
G.1010
defines
a
model
for
Multimedia Quality of Service (Multimedia QoS) category from the perspective of the end user. Taking into account the expectations of users for a variety of multimedia
29
applications, based on tolerance to information loss and delay, QoS Multimedia category identified. General Concept: A typical user is not concerned with how the technical implementation of a service. However, users will be able to compare the services offered by some service providers,
if
the
service
provider
offers
performance
parameters that are understood by users. There are three key parameters that affect the user's defined in ITU-T G.1010 [3], i.e.:
Delay: Delay can be defined in several ways, among others: (a) the period required to build service and (b) the period for receiving or sending information. The 30
delay has a very direct impact on user satisfaction. Technically, the size of the delay, depending on: (i) the type of service, (ii) the processing time at the terminal, network, and each server, and (iii) delaypropagation. Note that from a user perspective, the delay is a reflection of the ability of providers providing throughput to customers.
Delay variation or jitter: Delay variation is generally included as an important performance parameter, on the service is "real-time", as it was important at the transport layer of the communication data, which is based on packet-switched. However, on the service is "store and forward", is generally quite tolerant of delay 31
variation, it will usually take steps to reduce delay variation by way of buffering, effectively eliminating delay variation as perceived at the user level, but this will increase the delay.
Information loss: Information loss has a very direct effect
on
the
quality
of
the
information
finally
presented to the user, whether it is voice, image, video or data. In this context, information loss is not limited to the effects of bit errors or packet loss during transmission, but also includes the effects of any degradation introduced by media coding for more efficient transmission (e.g. the use of low bit-rate speech codecs for voice). 32
Quality & Performance Types Based on ITU-T Recommendation E.800 [5], quality & performance in the telecommunications field can be divided into several levels as follows:
33
General Concept of QoS. ITU-T Rec. E.800 provides a set of commonly used terms in the study and management of quality of service (QoS). The technical and non-technical terms related to the QoS listed and intended to represent the interests of all parties of telecommunications
service
market,
i.e.,
user,
service
provider, manufacturer and regulator. Here's an explanation of the classification:
NP (Network Performance): the performance of a network element. Typically, the NP is determined by assessing several technical parameters that describe the performance of a network element with reference 34
to some particular standard. NP Example: BER (Bit Error Ratio), Transmission Delay, processing time, jitter.
Overall Network Performance: The performance of all elements is integrated to form a network so that the network can be considered as a "black box" that will measure performance. For example, performance measurements
between
two
UNI
(User
Network
Interfaces).
End-to-end QoS: overall performance of the elements and processes involved in the chain of transmission of a
telecommunications
service
until
the
service
performed. QoS is measured from the point of view of 35
the user but does not involve the user in the process of measurement and assessment carried out objectively. Typically, QoS measurements depend on some typical characteristics of a telecommunications service.
QoE (Quality of Experience): overall performance of a telecommunications service by involving users in the process of measurement. QoE assessment is more subjective because it is influenced by the experience and
the
level
of
expectations
of
users
of
a
telecommunications service. In
particular,
the
difference
between
the
Network
Performance and QoS are described as follow:
36
To specify the end-to-end QoS, it is necessary to state the specified operating conditions in which a service is supported over a connection (= connectionless or connection oriented) that takes place. The QoS could also be altered for a given set of specified operating conditions by environmental conditions, such as traffic and routing.
Figure 3 illustrates the relationship between QoS and network network
performance
(NP).
performance
and
QoS
comprises
non-network
both
related
performance. Examples of NP are bit error rate, latency,
etc.,
and
for
non-network
performance
provision time, repair time, range of tariffs and 37
complaints resolution time, etc. The list of QoS criteria for a particular service would be dependent upon the service and their relevance could vary among the segments of the customer population In
general,
this
model
explains
the
following
two
dimensions:
The relationship between users and providers of telecommunications services
Expectation of QoS and QoS levels are in fact achieved for parties, customers and telecommunications service providers.
38
In the ITU-T Recommendation G.1000 [6], described the QoS model viewed from four different angles.
QoS Models
At a more detailed level, QoS can be divided into four viewpoints as illustrated in Figure 4. This concept is
39
described further in [ITU-T G.1000]. A generic definition of QoS is derived from a definition of quality and is given in clause 2. Of particular interest is QoS experienced by the user (expressed by QoSE or QoSP = QoS perceived). QoSE is influenced by the delivered QoS and the psychological factors influencing the perception of the user. Understanding of the QoSE is of primary importance to help optimize revenue and resources of the service provider.
40
Four different angles of QoS Model according to the ITU-T can be described as follows:
QoSR (QoS Required by the User). QoS needs of customers
are
usually
described
in
non-technical
parameters. A customer would expect the performance
41
of a telecommunication service without considering the technical aspects or limitations in the implementation of service.
QoSO (QoS Offered by the Service Provider). Telecommunications service provider mentioned QoS levels to be achieved. This can be done in two ways: o Non-technically, to allow users to understand the specifications given. o Technically,
in
order
to
facilitate
further
discussion with experts, the determination of the SLA, and facilitate the planning of a technical nature.
42
QoSD (QoS Delivered by the Service Provider). QoSD
reflect
the
level
of
QoS
that
has
been
successfully achieved by the telecom service providers. QoSD can test the ability of a telecommunications service provider to deliver the promised QoS.
QoSE (QoS Experienced by the User).
QoS
experienced by users reflect the subjective point of view
of
a
user
in
certain
circumstances
they
experienced. Customer satisfaction is one of the driving factors for this type of QoS. In general, QoSE described in nontechnical parameters. Telecom service providers can measure the level of QoSE by conducting a survey to its customers or to seek advice and input 43
from them. At this stage, a user combines personal experience with the expected technical quality of the service it uses. In addition to technological aspects, there are several other factors that affect the level of QoSE. Some of these factors such as starting from the signing of the contract between the user and the service provider, the service provider the ability to handle probleM faced by customers, and the overall relationship between the customer and the service provider. Thus, it can be concluded that QoSE quite difficult to measure because there are several factors "hidden" are not easy to identify.
44
User Perception of QoS vs Operational Performance in Practical [1] Why
are
any
differences
between
the
results
of
measurements of QoSE (QoS Experience by the user) and QoSD
(QoS
Delivered
by
the
provider),
whereas
the
measurement of QoS and network performance are not contradictory? In practice, many factors that influence the customer's perception of the QoS service they received from the provider. In general, the perception of the customer is to compare the quality of service that they feel with the quality they expect.
45
Customer expectations are influenced by the rates they pay and the information that they know from the media and from books. In general, if a customer feels an expensive, then their expectations for service quality is high as well. Provider of telecommunications equipment owned or rented, and operates with the standard of performance they called KPI (Key Performance Indicator). The better prepared KPI, and the more realistic service rates, the correlation between customer expectations for QoS performance telecommunications systeM, will increase. To better understand the expectations of its customers, the provider must have good customer service. Customer service 46
should
be
a
very
good
understanding
of
operational
performance measured through Key Performance Indicators, as well as understand the relationship between customer complaints with performance indicators. The task is customer service is two-way. On the one hand, they should be able to answer customer complaints properly, according to the technical conditions of operation. On the other hand, they should be able to give direction to the company, the translation of the customer's wishes into technical performance criteria. Providers that are less, in general, ignore the customer service. As a result, customers will be frustrated. Customers 47
have been disappointed, because he felt the complaint was not answered correctly. Provider engineers also depressed, because it was already successfully operate the device in accordance with technical standards, but it is still considered bad by the company who read so many reports of customer disappointment.
48
Grade of Service ITU-T Recommendation E.771 proposes network Grade of Service (GOS) parameters for current and evolving land mobile services. These parameters are defined, and their target values specified, assuming that the network and the network components are operating in their normal mode (i.e. are fully operational). Further, the parameters and their target values assume normal (as opposed to distress or emergency) traffic. In
this
Recommendation,
the
following
traffic
GOS
parameters are specified for mobile circuit switched services:
49
Post Selection Delay: defined as the time interval from the instant the first bit of the initial SETUP message containing all the selection digits is passed by the calling terminal to the access Signaling system until the last bit of the first message indicating ccall disposition
is
received
by
the
calling
terminal
(ALERTING message in case of successful call).
Answer signal delay: defined as the time interval from the instant that the called terminal passes the first bit of the CONNECT message to its access Signaling system until the last bit of the CONNECT message is received by the calling terminal.
50
Call release delay: defined as the time interval from the instant the DISCONNECT message is passed by the user terminal which terminated the call to the access Signaling system, until the RELEASE message is received by the same terminal (indicating that the terminals can initiate/receive a new call).
Probability of end-to-end blocking: defined as the probability that any call attempt will be unsuccessful due to a lack of network resources.
Probability
of
unsuccessful
land
cellular
handover: defined as the probability that a handover attempt fails because of lack of radio resources in the target cell, or because of a lack of free resources for 51
establishing the new network connection. The failure condition is based either on a specified time interval since the handover request was first issued or on a threshold on signal strength.
The Concept of QoS by ETSI [2] ETSI standard TS 102 250-2 v2.2.1 (2011) covering the QoS aspects for popular services in GSM and 3G networks. The standard divided into 6 parts book that identified below: •
ETSI TS 102 250 Part 1 identifies QoS criteria for popular services in GSM and 3G networks. They are considered to be suitable for the quantitative characterization of the
52
dominant technical QoS aspects as experienced from the customer perspective. •
ETSI TS 102 250 Part 2 defines QoS parameters and their computation
for
popular
services
in
GSM
and
3G
networks. •
ETSI TS 102 250 Part 3 describes typical procedures used for QoS measurements over GSM, along with settings and parameters for such measurements.
•
ETSI
TS
102
250
Part
4
defines
the
minimum
requirements of QoS measurement equipment for GSM and 3G
53
•
ETSI TS 102 250 Part 5 specifies test profiles which are required to enable benchmarking of different GSM or 3G networks both within and outside national boundaries.
•
ETSI TS 102 250 Part 6 describes procedures to be used for statistical calculations in the field of QoS measurement of GSM and 3G networks using probing systems.
General Consideration: ETSI identifies QoS criteria for popular services in GSM and 3G. They are considered to be suitable for the quantitative characterization of the dominant technical QoS aspects as experienced from the customer perspective. The criteria are described by their name and a short description from the customer point of view. The
54
relationship between customer satisfaction, QoS and NP is shown in figure 1. Phases of Service from the Customer's Point of View
55
Figure shows different phases (Quality of Service aspects) during service use from the customer’s point of view.
The five QoS aspects are: 1. Network
Availability:
is
the
probability
of
a
telecommunications service that can be offered to customers through a network infrastructure. 2. Network Accessibility: probability that users can register on the network to be successful so that the network
can
provide
telecommunication
services. 56
Network can only be accessed when it is available to the user. 3. Service Accessibility: probability that the user can access the service you want to use., If the customer wants to use a service, the network operator should provide him as fast as possible access to the service 4. Service Integrity: describes QoS while using the service, and contains elements such as the quality of the content being transmitted, such as sound quality, video quality, and the number of bits transmitted error in the file. Service integrity can only be calculated if the service is accessible to success.
57
5. Service Retainability: Service retainability describes the termination of services, in accordance with or against the will of the user. Explains how to end or terminate a service, whether or not the will of the user. Examples of service retain ability parameter are call cut-off ratio or the data cut-off ratio.
3GPP Concept of QoS [7] The book of 3GPP Standard TS 23.207
provides the
framework for end-to-end GPRS and UMTS. The end-to-end QoS architecture is provided in Figure 7. The book describes the
interaction
between
the
TE/MT
(Terminal
Equipment/Mobile Terminal) Local Bearer Service, the GPRS 58
Bearer Service, and the External Bearer Service, and how these together provide Quality of Service for the End-to-End Service. The book also describes IP level mechanisms necessary in providing end-to-end Quality of Service and possible interaction between the IP level and the GPRS level, as well as the application level and the IP level. This book covers different architectural aspects of the endto-end Quality of Service concept and architecture with varying level of detail. In general, other specifications shall be referred to for further details; these other specifications enable the reader to acquire the full understanding of the end-to-end Quality of Service concept and architecture.
59
60
QoS Management Functions in the Network: to provide IP QoS end-to-end, it is necessary to manage the QoS within each domain. An IP BS (Base Station) Manager is used to control the external IP bearer service. Due to the different techniques used within the IP network, this communicates to the UMTS BS manager through the Translation function. The QoS management functions for controlling the external IP bearer services and how they relate to the UMTS bearer service QoS management functions are shown in Figure 8. QoS Conceptual Model: there are many different end-toend scenarios that may occur from an UE connected to an UTMS network. The following examples depict how end-to-
61
end QoS will be delivered for a number of scenarios that are considered to be significant.
62
NOTES:
Although the backbone IP network is shown as a single domain, it may consist of a number of separate domains.
The structure of the Local UE is not specified. It includes cases from a simple host, to a gateway to a 63
network such as a LAN. If the UE is acting as a gateway, it is responsible for providing the IP BS Management towards the extended network.
The remote side is shown as a simple host. Other more complex cases on the remote side such as a private LAN with over-provisioning, or possibly LAN priority marking, and DiffServ and/or RSVP capable routing elements is not depicted. It is envisaged however that interworking between the QoS mechanisms in a more complex remote user side could also be performed with some similarities to the mechanisms shown at the local side.
64
Scenarios: these scenarios give examples of concatenating QoS mechanisms in different parts of the network which together can deliver an end-to-end QoS. These scenarios are not intended to describe the details of the interworking between the QoS mechanisms. The different scenarios involve cases with and without service based local policy. Each scenario describes the applicable cases, possibly by referencing another scenario. In some scenarios, only one of the cases may be valid (e.g. scenario 5). Where both cases are covered, they may be described together identifying the optionality, or separately for clarity of the individual cases.
65
Scenario 1: Local UE does not provide an IP BS Manager The UE does not provide an IP BS Manager. The end-to-end IP QoS bearer service towards the remote terminal is controlled from the GGSN. The scenario assumes that the GGSN supports DiffServ functions, and the backbone IP network is DiffServ enabled. In this scenario, the control of the QoS over the UMTS access network (from the UE to the GGSN) may be performed either from the terminal using the PDP context signaling or from the SGSN by subscription data. The IP QoS for the downlink direction is controlled by the remote terminal up to the GGSN. The GGSN will apply receiver control DiffServ edge functions and can reclassify
66
the data (remarking the DiffServ Code Point = DSCP). This may affect the QoS applied to the data over the UMTS access (the TFT may use the DSCP to identify the data to be allocated to the PDP context). The end-to-end QoS is provided by a local mechanism in the UE, the PDP context over the UMTS access network, DiffServ through the backbone IP network, and DiffServ in the remote access network in the scenario shown in the figure below. The GGSN provides the interworking between the PDP context and the DiffServ function. However, the interworking may use information about the PDP context which is established,
or
be
controlled
from
static
profiles,
or
dynamically through other means such as proprietary of 67
HTTP
based
mechanisms.
The
UE
is
expected
to
be
responsible for the control of the PDP context, but this may instead be controlled from the SGSN by subscription.
68
Scenario 2: Local UE supports DiffServ The UE performs an IP BS function which enables end-to-end QoS without IP layer signaling towards the IP BS function in the GGSN, or the remote terminal. The scenario assumes that the UE and GGSN support DiffServ edge functions, and that the backbone IP network is DiffServ enabled. In this scenario, the control of the QoS over the UMTS access network (from the UE to the GGSN) may be performed either from the terminal using the PDP context Signaling.
Alternatively, subscription data accessed by the
SGSN may override the QoS requested via Signaling from the UE. 69
In this scenario, the terminal supports DiffServ to control the IP QoS through the backbone IP network. The IP QoS for the downlink direction is controlled by the remote terminal up to the GGSN. The PDP context controls the QoS between the GGSN and the UE. The UE may apply DiffServ edge functions to provide the DiffServ receiver control. Otherwise, the DiffServ marking from the GGSN will determine the IP QoS applicable at the UE. The end-to-end QoS is provided by a local mechanism in the UE, the PDP context over the UMTS access network, DiffServ through the backbone IP network, and DiffServ in the remote access network in the scenario shown in the figure
70
below. The UE provides control of the DiffServ, and therefore determines the appropriate interworking between the PDP context and DiffServ. The GGSN DiffServ edge function may overwrite the DSCP received from the UE, possibly using information regarding the PDP context which is signaled between the UMTS BS managers and provided through the translation/mapping function to the IP BS Manager.
71
Scenario 3: Local UE supports RSVP Signaling with IntServ semantics, and DiffServ; without service based policy The UE performs an IP BS function which enables end-to-end QoS using IP layer signaling towards the remote end. There 72
is no IP layer signaling between the IP BS Managers in the UE and the GGSN. However, the GGSN may make use of information regarding the PDP context which is signalled between the UMTS BS managers and provided through the translation/mapping function. This scenario assumes that the UE and GGSN support DiffServ edge functions, and that the backbone IP network is DiffServ
enabled.
In
addition,
the
UE
supports
RSVP
Signaling which interworks within the UE to control the DiffServ. The application layer (e.g. SIP/SDP) between the end hosts identifies the QoS requirements. The QoS requirements from application layer are mapped down to create an RSVP 73
session. The UE shall establish the PDP context suitable for support of the RSVP session. The authorization token from the application layer when included shall be mapped to the PDP context parameters, and may also be mapped to the RSVP signaling. In this scenario, the control of the QoS over the UMTS access network (from the UE to the GGSN) may be performed either from the terminal using the PDP context Signaling.
Alternatively, subscription data accessed by the
SGSN may override the QoS requested via Signaling from the UE. In this scenario, the terminal supports Signaling via the RSVP protocol to control the QoS at the local and remote accesses, and DiffServ to control the IP QoS through the 74
backbone IP network. The RSVP Signaling protocol may be used for different services. It is expected that only RSVP using the Integrated Services (IntServ) semantics would be supported, although in the future, new service definitions and semantics may be introduced. The entities that are supporting the RSVP Signaling should act according to the IETF
specifications
interwork.
for
IntServ
and
IntServ/DiffServ
The QoS for the wireless access is provided by
the PDP context. The UE may control the wireless QoS through Signaling for the PDP context. The characteristics for the PDP context may be derived from the RSVP signaling information, or may use other information.
75
QoS for the IP layer is performed at two levels. The end-toend QoS is controlled by the RSVP Signaling. Although RSVP Signaling can be used end-to-end in the QoS model, it is not necessarily supported by all intermediate nodes. Instead, DiffServ is used to provide the QoS throughout the backbone IP network. At the UE, the data is also classified for DiffServ. Intermediate QoS domains may apply QoS according to either
the
mechanisms.
RSVP In
Signaling this
information
scenario,
the
UE
or is
DiffServ providing
interworking between the RSVP and DiffServ domains. The GGSN may override the DiffServ setting from the UE. This GGSN may use information regarding the PDP context in
76
order to select the appropriate DiffServ setting to apply, as shown in the figure 12.
77
Scenario 4: Local UE supports RSVP Signaling with IntServ semantics, and DiffServ; where service based policy is applied The UE performs an IP BS function which enables end-to-end QoS using IP layer signaling towards the remote end. However, the UE relies on this end-to-end communication being utilised by at least the access point (GGSN) in order to provide the end-to-end QoS. This scenario assumes that the UE and GGSN support RSVP signaling which may control the QoS directly, or interwork with DiffServ. The backbone IP network is RSVP and/or DiffServ enabled. The application layer (e.g. SIP/SDP) between the end hosts identifies the QoS requirements. The QoS requirements from application layer are mapped down to create an RSVP session. The UE shall establish the PDP context suitable for 78
support of the RSVP session. The authorization token from the application layer shall be mapped to the PDP context parameters, and may also be mapped to the RSVP Signaling. In this scenario, the terminal supports Signaling via the RSVP protocol to control the QoS across the end-to-end path. The GGSN also supports the RSVP Signaling, and uses this information rather than the PDP context to control the QoS through the backbone IP network. The control of the QoS through the core is expected to be supported through interworking with DiffServ at the GGSN, although it may optionally be supported by per flow resource reservation. The RSVP Signaling protocol may be used for different services. It is only expected that only RSVP using the 79
Integrated Services (IntServ) semantics would be supported, although in the future, new service definitions and semantics may be introduced. The entities that are supporting the RSVP Signaling may fully support the specifications for IntServ and IntServ/DiffServ interwork. If not, they are expected to set the break bit. In this scenario, the control of the QoS over the UMTS access network (from the UE to the GGSN) may be performed either from the terminal using the PDP context Signaling. Alternatively, subscription data accessed by the SGSN may override the QoS requested via Signaling from the UE.
80
QoS for the IP layer is performed at two levels. The end-toend QoS is controlled by the RSVP Signaling. Although RSVP Signaling take place in the QoS model, it is not necessarily supported by all intermediate nodes. DiffServ is used to provide the QoS throughout the backbone IP network, although optionally each node may support RSVP Signaling and allocation of resources per flow. An authorization token may be included in the RSVP Signaling and the PDP context establishment/modification. The GGSN may authorize the RSVP
session
and
configure
the
Diffserv
classifier
functionality. The GGSN supports the RSVP Signaling and acts as the interworking point between RSVP and DiffServ.
81
Intermediate QoS domains may apply QoS according to either the RSVP or DiffServ mechanisms. The end-to-end QoS is provided by a local mechanism in the UE, the PDP context over the UMTS access network, DiffServ through the backbone IP network, and RSVP in the remote access network in the scenario shown in the figure below. The RSVP Signaling may control the QoS at the local access. This function may be used to determine the characteristics for the PDP context, so the UE may perform the interwork between RSVP and the PDP context.
82
Scenario 5: Local UE supports RSVP Signaling using IntServ Semantics In this scenario, the control of the QoS over the UMTS access network (from the UE to the GGSN) may be
83
performed
from
the
terminal
using
the
PDP
context
Signaling. Alternatively, subscription data accessed by the SGSN may override the QoS requested via Signaling from the UE. The QoS for the downlink direction is controlled by the remote host from the remote network to the GGSN. The PDP context controls the UMTS level QoS between the GGSN and the UE. The QoS in the uplink direction is controlled by the PDP context up to the GGSN. The GGSN configures the DiffServ Edge function to interwork with the backbone IP network and control the IP QoS bearer service towards the remote -host.The end-to-end QoS is provided by a local mechanism in the UE, the PDP context over the UMTS access network, DiffServ through the backbone IP network, and 84
DiffServ in the remote access network. Note that DiffServ control at the Remote Host is shown in this example. However, other mechanisms may be used at the remote end, as demonstrated in the other scenarios.
85
Scenario 6: Local UE provides authorization token in PDP context activation/modification message and GGSN provides interworking with DiffServ The UE performs an IP BS function which enables end-to-end QoS without IP layer Signaling and negotiation towards the IP BS function in the GGSN, or the remote host. The P-CSCF provides the authorization token to the UE during the SIP session setup process, and the UE provides the authorization token to the GGSN in the PDP context activation/modification message. The GGSN uses the authorization token to obtain a policy decision from the PCSCF (PDF). This is done via the standardized interface between the PDF and GGSN. Even if the interface is an open interface where all information elements
are
standardized,
the
actual
usage
of
the 86
information is operator specific. The scenario assumes that the GGSN support DiffServ edge functions, and that the backbone IP network is DiffServ enabled.
GSM Association QoS Theory [4] GSM
Association
parameters definitions
and given
standard their in
this
PRD
IR.42,
computation. book
are
The
defines
QoS
harmonized
considered
as
the
prerequisites for comparison of QoS measurements and measurement results. General Consideration: all the defined quality of service parameters and their computations are based on field measurements. That indicates that the measurements were 87
made
from
customers
point
of
view
(full
End-to-End
perspective, taking into account the needs of testing). It is assumed that the end customer can handle his mobile and the services he wants to use (operability is not evaluated at this time). For the purpose of measurement it is assumed
that the service is available and not barred for any reason
routing is defined correctly without errors and
The target subscriber equipment is ready to answer the call.
88
Voice quality values measured should only be employed by calls ended successfully for statistical analysis. However, measured values from calls ended unsuccessfully (e.g. dropped) should be available for additional evaluations and therefore, must be stored. Quality of Service Parameter Definition, and Their Computation The following Figure 15 shows a model for quality of service parameters. This model has three layers. The first layer is the Network Access, the basic requirement for all the other QoS aspects and QoS parameters. The outcome of this layer is the QoS parameter Network Accessibility.
89
The second layer contains the other three QoS aspects Service Access, Service Integrity and Service Retainability. The different services are located in the third layer. Their outcome is the QoS parameters.
90
Chapter 2: Procedure of Key Performance Indicators Determination Technical and business strategy to determine the QoS by telecom operators will be discussed here. But it will not be discussed when based on considerations of politics. Technical considerations determining the QoS is also very complicated, as it include the selection of transport technology, topology, and reliability of the device. First, providers should develop a KPI (Key Performance Indicator). KPI arranged on several considerations.
91
The 1st consideration is the international standard and recommendation of the ITU-T, ETSI, IEEE, ANSI and others.
The 2nd Comparing standards of various telecom operators and National Regulatory Bodies in the world.
The 3rd consideration is the National Regulatory Body in each country, And,
The
4th
consideration
is
the
SLA
(service
level
agreement) between providers and customers. ITU-T is an agency under the United Nations, thus being the most fair of reference materials, all member countries, should pay attention to the recommendations they make. But the ITU-T Recommendations are so many; every 92
provider should have some staff, which specifically follows the development of the recommendations issued by the ITU, particularly
with
respect
to
the
performance
of
telecommunications networks and services. There are some kinds of cellular network in the world; one that is widely used is the GSM standard. In this book many referenced
international
standards
related
to
GSM
technology, including ETSI, 3GPP and GSMA. Telecommunications regulatory body in each country has different qualities, the regulator is good, and they were able to
formulate
the
rules
of
good
performance
of
telecommunications services and must be obeyed by every 93
provider. A good rule is, able to be met by the provider while satisfying customers. It's also not an easy job. Customer satisfaction is also influenced by the rates they pay. For example, customers will complain the service providers when they pay more expensive than other provider’s rates, whereas
at
other
providers
who
charge
less,
the
performance is worse, and no one complained. SLA is one of the reasons that the provider should monitor traffic at every moment, in every place and at every service. Through SLA, the provider promises to serve customers by meeting specific performance requirements, and they get
94
paid, if the SLA is not met, the payment cannot be obtained, it may even have to pay a penalty to its customers.
Target Values After
selecting KPI parameters, we then have
to be
determined from the target value of each parameter. Determination of target values, not things that are certainly applicable in a long time. Often the target values should be changed, adapted to the circumstances that occurred. Here are some guidelines for determining the target values:
The target value of the KPI provider parameters should be higher than the target value set by the regulatory body. For example, regulators set a target for 90% of 95
SMS end-to-end delay is not allowed to exceed 1 minute, then the provider setting 30 seconds.
Each period, about 6 months to 1 year, the target values should be evaluated. *
The target value should be increased, if the
target is too easy to be reached by the provider or, if there are many complaints from customers. *
The target value may be derived, for example, if
inflation is rises, the income per capita is declining; investment is rising and other causes.
Regulators will probably set a target value for a particular provider, which is different than any other
96
provider. The target value should be higher, if the tariff is more expensive. Examples of QoS parameters contained in the ITU-T and ETSI standards can be selected as a Key Performance Indicator, shown in the following table. Table 1 Example of Key Performance Indicators and Target values (1 of 2) Target Value
Type of Service Network Accessibility
Telephony Network
Examples of QoS Parameter Indicator
The Worst
The Best
NER (Network Effectiveness Ratio) SCR (Successful Call Ratio)
20 %
2%
25 %
3%
CCR (Call Completion ratio)
30 %
5%
20 %
2%
NNGoS (End to end Grade of Service)
97
Mobile Telephony Network Accessibility
Location Update Success Rate
5 sec
1 msec
Handover Success Rate
10 %
99.99 %
Radio Network Unavailability
20 %
0.0001 %
< 128 kbps
>1 Mbps
Mean Data Rate
Table 1 Example of Key Performance Indicators and Target values (2 of 2) Target Value
Type of Service
Telephony Service
SMS (Short Message Service) Internet Service
Examples of QoS Parameter Indicator Telephony Setup Time [s], In the past, often referred to as PDD (Post Dial Delay) Telephony Speech Quality or MoS (Mean Opinion Score) Telephony Cut-off Ratio SMS End-to-End Delivery Time Completion Rate or SMS loss Percentage HTTP Service Non-Accessibility HTTP Session Failure Ratio
The Worst
The Best
10 sec
100 msec
1.5
3.25
20 % 5 min
0.0001 % 1 sec
3%
0.0001 %
10 % 10 %
0.0001 % 0.0001 %
98
FTP {Download.Upload} Service Non-Accessibility FTP {Download Upload} Session Failure Ratio E-Mail {Upload|Download} Login Non Accessibility E-mail {Upload|Download} Session Failure Ratio Ping Round Trip Time Streaming Service NonAccessibility Streaming Reproduction Cutoff Ratio
20 %
0.01 %
20 %
0.01 %
10 %
0.0001 %
10 % 10 % 2 sec
0.0001 % 0.0001 % 10 msec
20 %
0.01 %
10 %
0.0001 %
World standard vs. Regional Standards In Chapter 1, the QoS theory
of various international
standards bodies has been elaborated. The most complicated problem for national regulators and providers is choosing whether to use the world standard (ITU-T) or regional standards such as ETSI. 99
Although the ITU-T and ETSI have no difference in terms of the framework, but there are some different in details. My recommendation is to minimize the QoS parameters were selected
as
parameters
Key
Performance
Indicators.
Only
QoS
which directly related to the QoE will be
selected.
Study of Key Performance Indicators from various countries around the world. Here presented data on Key Performance Indicator of 3 operators, ie: Telecom Italy, Vodafone, and BT Telecom, as well as 6 regulator from 6 countries, i.e.: Singapore, India, USA, Nigeria, Indonesia, Malaysia.
100
From my observation about the quality of service especially for
mobile
telecom
services
provider,
acquired
some
important findings as follows:
QoS standards of telecom operators are generally nontechnical QoS, such as Quality of Experience (by Vodafone), or MOS using PESQ (by BT), or related service quality (by Telecom Italia). It shows that they prefer
to
flaunt
Assessment
of
success
QoS.
in
Not
terms in
terms
of of
Customer network
performance
To ensure that operators provide good service to its customers, the regulators issued a binding provision.
101
Regulator requires that operators meet some basic parameters, which are accompanied by a minimum target to be achieved, and the operator shall report to the regulator periodically. Regulations are generally prepared to follow existing international standards and adapted to the market conditions of each country. QoS parameters issued by the regulator, there are technical and some are non-technical. Summary of identification result for some benchmarking data is provided in the following table.
102
Table 2 the Qos Parameters of some telecom operators and national regulatory bodies (1 of 3) Institution Telecom Italy
Vodafone BT Telecom IDA (Singapore Regulatory)
QoS Parameter or Framework • Activation time of services • Malfunctioning rate of services for access to broadband internet • Repair time for services for access to broadband internet • Answer times to calls to customer assistance services • Bills challenged • Quality of Customer Experience • Quality Indicators for End Users Customer Care Services • MOS using PESQ (adopted from BT Report Assessment for his vendor) • Service Coverage (for Compliance) • Network availability • Network Congestion During Busy Hour • Success rate for PSTN and Mobile Originated Calls • Average Call Set-up time for • Drop call rate of PSTN and mobile originated calls during busy hour • Complaints on coverage per 1000 subscriber 103
Table 2 the Qos Parameters of some telecom operators and national regulatory bodies (2 of 3) Institution India Regulatory
USA
QoS Parameter or Framework • • • • • • • • • •
Nigeria Comm. Commission* (*: noted here that there are
• • • •
Network availability Connection Establishment (Accessibility) Connection Maintenance (Retainability) POI Metering and Billing Response time to the customer for assistance Termination services No specific requirement Each operator must determine the final implementation of their QoS and Policy based on their own business Recommends service providers implement a policy management framework based on 3GPP Rel-7 Policy Charging Control Call Setup Success Rate (%) Call Drop rate (%) Handover Success Rate (%) Post Dialing Delay (s) 104
lots of complete telecommunicati on standard books in countries in Africa)
• • • • • • • • •
Transmission Impairment Other Network Measures % of SMS / MMS delivery failures % of SMS / MMS incorrect feedback % of SMS / MMS multiple billing Complaints Speed of Problem Resolution Billing Integrity Customer Care Accessibility
Table 2 the Qos Parameters of some telecom operators and national regulatory bodies (3 of 3) Institution Indonesia Regulatory
Malaysia Regulatory
QoS Parameter or Framework • • • • • • •
Standards Performance of Billing Standards of Compliance Application Activation Standards for Public Complaints Handling Customer Standards level disturbance report Standards of Service Level Call Center Performance Standards of the Short Message Service Service Accessibility Ratio – Packet Switched Data (SAPSD) 105
• IP-Service Access Ratio (IPSA-PSD) • Completed Session Ratio – Packet Switched Data (CoSeR-PSD)
106
Chapter 3: Details of QoS parameters in the Various International Standards There
are
many
international
standards
for
telecommunication quality and experience. In this book will be written summary. The essence of international standard related to the QoS parameter are:
A variety of QoS parameters for each service is determined by world & regional standard bodies such as ITU-T, ETSI, 3GPP, GSM Association etc. referring
107
to the international standard, each national regulatory bodies make up their own definition of KPI.
Each international standard bodies may have different definition of QoS parameters. Contrary, there are the same
standards,
but
rewritten,
such
as:
ITU-T
Recommendation E.802 is the sama as ETSI Standard EG 202 057. Table 3 Number of QoS parameters contained in the international standards
Service Category
Numbe r of KPI
ETS I EG 202 057 9
ETS I TS 102 250 22
ITU T E.80 0
78
ETS I EG 202 009 7
Telephony & Video Telephony SMS & MMS Internet
GSM A PRD IR.42 12
ITU-T E.77 1
3GP P 52 402
0
3GP P TS 32 410 36
4
0
15 119
0 19
3 10
12 77
0 0
0 0
4 6
0 0
0 0 108
Customer Support & Maintenanc e Total
26
13
14
0
0
0
0
0
0
238
39
39
111
0
36
22
4
0
Summary of our studies, described below
ITU-T QoS Parameters In the ITU-T RecommendationE.800, quality of service terms have been classified into three broad areas; service, network and management.
Table 4 Quality of Service Terms in ITU-T E.800 [5], [6] (1 of 2)
Service QoS Parameters Service-provision Call setup
Network QoS Parameters Customer premises equipment Network/user interface
Management QoS Parameters QoS resource management Class of service 109
Call progress
Interconnection
Service restoration/repair Service quality characteristics Charging & Billing
Network accessibility
Customer relationship management Benchmark
Connection accessibility
Compensation schemes
Connection establishment error probability Connection establishment failure probability Unacceptable transmission probability No tone probability
Service level agreement (SLA) Service quality agreement (SQA) Time between interruptions Interruption duration
Misrouting probability
Mean time between interruptions Mean time to restoration, Mean time to recovery, Mean time to repair
Common Service-specific terms Security-specific terms
Traffic ability performance
Table 4 Quality of Service Terms in ITU-T E.800 [5], [6] (2 of 2)
Service QoS Parameters
Network QoS Parameters Transmission performance
Management QoS Parameters Fault coverage 110
Bit transparency Bit error ratio (BER) Error free seconds ratio Propagation performance End-to-end IP network End-to-end IP network performance Percent IP service availability (PIA) Release failure probability Connection clearing failure probability Connection establishment success ratio (CESR)
Repair coverage Fault Corrective maintenance repair Reliability performance Failure rate acceleration factor Disaster recovery, Business continuity Complaint Discovery service
Table 5, provides an indication of suitable performance targets for audio and video applications.
111
Table 5 the ITU-T Performance targets for audio and video applications [5], [6] (1 of 2)
Mediu m
Application
Degree of Symme try
Typic al Data Rates
Key Performance Parameters & Target Values
One-way delay
Conversati onal voice
Twoway
4-64 kbit/ s
Audio
Voice messaging
Primar ily oneway
4-31 kbit/ s
Audio
High quality streaming audio
Primar ily oneway
16128 kbit/ s (Not e 3)
Audio
