La importancia de los modelos y procedimientos para la planificación, seguimiento y control en la...

Colombia, 23-24 September 2013

The importance of models and procedures for planning, monitoring and control in the

provision of communications services

Dr.-Ing. H. W. Gierlich

Head of Telecom Division

CITEL (PCC.I)/ ITU Forum on Information and

Communication Technology Service:

Quality, Control and Surveillance

(Cartagena de Indias, Colombia, 23-24 September 2013)

Colombia, 23-24 September 2013 2

Outline

Introduction

Communication Services –Underlying System configurations

Planning: The ITU-T E-model (G.107 & G.108)

Network Monitoring: P.862, P.863 & P.563

Wideband – The new Challenge

Summary

ITU-T: QoS and QoE

Quality of Service (QoS):

Totality of characteristics of a telecommunications service that bear on its ability to satisfy stated and implied needs of the user of the service.

Quality of Experience (QoE):

The overall acceptability of an application or service, as perceived subjectively by the end-user.Quality of experience includes the complete end-to-end system effects (client, terminal, network, services infrastructure, etc.).

Overall acceptability may be influenced by user expectations and context.


Speech Quality –what we would like to have


1m

“orthotelefonic reference position”

Speech Quality…


speechquality

talkingsituation

listeningsituation

conversationalsituation

… from the user’s perspective

End to End Conifguration


ISCDSL ISC PBX GW

PSTN

1-15 ms240 ms

MSC BSS

90-120 ms

IP-GW

Netw. 1

IP-GW

10 - 400 ms10 - 400 ms

add. 1 - 100 ms !

Netw. 2

Impact on speech quality:- delay now time variant

- echo much more dominant

- Coding distortion

- background noise problems

- insufficient quality of the analog network components (att., noise, distortion…)

- insufficient quality of acoustical components

A big problem of today‘s networks, interconnection & terminals : delay – unpredictable, load

dependant, time variant

Contributions to Quality

The networks

Type of networks

Interconnection

QoS management

The endpoints

Types of terminals

Interoperability

Terminal – Network

Terminal – Terminal

The users‘ location

Environmental conditions


• Network planning

• Network monitoring

• Laboratory terminal testing

• Interoperabilitytesting


Outline

Introduction





Summary

Reference Connection in the E-model


Transmission Rating in the E-model

Rating factor R:

With:

R0 – Basic signal to noise ratio (takes into

account circuit noise, room noises)

Ix – Impairment factors (see next slide)

A – Advantage factor (takes into account a

potential advantage for a user for a specific transmission in a specific situation)


AIe-effIdIsRoR +−−−=

Basic assumption: Psychological factors on the psychological scale are additive

Network planning & E-model (ITU-T G.107 & G.108)

Basis of the E-model: Impairment factors

Simultaneous impairment factor Is (non

optimum loudness rating, non optimum sidetone, PCM coding distortion)

Delayed impairment factor Id (impact of

delay, talker- or listener echo)

Equipment impairment factor Ie (all types

of impairments in equipment such as coding distortion including the effect of packet loss)


How to derive Ie?

Ie is based on subjective tests and can be derived as follows:

Equipment impairment factors for the most popular codecs in ITU-T G.113

From subjective listening tests described in ITU-T P.833

From objective models (e.g. ITU-T P.863) following the procedure in ITU-T P. 834


Some Ie factors from G.113


Codec type ReferenceOperating

rate[kbit/s]

Ievalue

PCM (see Note) G.711 64 0ADPCM G.726, G.727 40 2

G.721, G.726, G.727 32 7G.726, G.727 24 25G.726, G.727 16 50

LD-CELP G.728 16 712.8 20

CS-ACELP G.729 8 10G.729-A + VAD 8 11

RPE-LTP GSM 06.10, full-rate 13 20VSELP GSM 06.20, half-rate 5.6 23ACELP GSM 06.60,

enhanced full rate12.2 5

ACELP G.723.1 5.3 19MP-MLQ G.723.1 6.3 15

The E-model Prediction Range

R – value range: prediction on a scale

Mapping to MOS:

For R < 0:

For 0 < R < 100:

For R > 100:


1000 <<R

1MOSCQE =

6CQE 107)100)(60(035.01MOS −⋅−−++= RRRR

5.4MOSCQE

=

Guide for User Satisfaction based on R-values


Range of E-Model Rating R

Speech transmission

quality category

User satisfaction

90 ≤ R < 100 Best Very satisfied80 ≤ R < 90 High Satisfied70 ≤ R < 80 Medium Some users

dissatisfied60 ≤ R < 70 Low Many users

dissatisfied50 ≤ R < 60 Poor Nearly all users

dissatisfiedConnections with E-Model Ratings R below 50 are not recommended.

Guide on Transmission Planning: ITU-T G.108

Demonstrates the application of the E-model for end-to-end transmission planning in a wide range of networks

Keep in mind: G.107 and G.108 are applicable for narrowband networks



Outline

Introduction





Summary

Networks & Network Monitoring

Main network related impairments:

Delay

Delay variation (jitter)

Listening speech impairment due to

Coding

Transcoding

Interconnection

Packet loss/jitter


ITU-T Models for Perceptual based Speech Quality Measurement

ITU-T P.862 (2001): PESQ

ITU-T P.863 (2011): POLQA

The basic principle:


Typical Processing Steps (Schematic):

Adaptation Hearing Model

Comparison,Reference,Reduction,Signal Value

Results ofListening Tests!

S indexQ

Speech Signal

Test Object Hearing Modelprocessed

signal

reference signal

Principle

Intrusive test procedure

Objective prediction of MOS (mean opinion score) as achieved in listening test subjectively

Prediction on a MOS-scale:MOS 5 – excellent

MOS 4 – good

MOS 3 – fair

MOS 2 – poor

MOS 1 – bad

Substitution of subjective tests for known codecs and impairments


Application

Intrusive testing:

Insertion of a reference speech sequence

Acquiring the transmitted, distorted speech sequence

Calculation of the speech quality by comparing to the reference

Output: MOS LQOn – mean opinion score, objective, narrowband


Typical setups


Central server- automated call setup- generation of test

sequences- analysis & statistics

FixedNetwork

Probe @ NTP- automated call

setup- generation of

test sequences

Probe @ NTP- automated call


test sequences

Mobile Network

Mobile Probe - automated call


test sequences

Mobile Probe - automated call


test sequencesFixed

Network 2

Very difficult in monitoring: network one way transmission

delay

Not Intrusive Testing - ITU-T P.563

Listening speech quality prediction based on speech signal in a call

No reference file insertion required

Average listening speech quality prediction on statistical evaluation of a high number of calls on the same connection

Not recommended for test on a call by call basis

Much less reliable than intrusive testing based on P.862 and P.863


The wideband challenge

High quality expectation by the user

Wideband must be significantly better in all quality aspects

Significant contribution to quality by the terminals

First attemt to certify high quality wideband speech transmission: GSMA


Wideband listening examples


(.wav)

Fullband

Narrowband

Wideband

Mobile Phone

Mobile signal

processingRF-Interface

air interface

SpeechTranscoder

speech

noise

Wideband (.wav)

Narrowband (.wav)…in noise

Wideband Network Planning –ITU-T G.107.1

The principle of the model is identical to the narrowband version G.107

The model reflects the improvements in quality in wideband:

Maximum R = 129 (instead of 100 for narrowband)

Model provides new wideband R calculation mapping R to the range of 0-100

All factors – R0 and Impairment factors are adapted accordingly


Wideband Network Monitoring

Setup as in narrowband

Only intrusive testing available

Network monitoring is based on ITU-T P.863 POLQA

ITU-T P.862 PESQ should not be used in wideband


Conclusions and Recommendations

ITU-T provides models for planning and monitoring

Network planning is essential for achieving high network QoS

Network monitoring is essential to detect potential issues – e.g. changing radio conditions, changing network conditions (jitter, packet loss)

Both is not sufficient to guarantee a good QoE – terminals play a major role for the overall speech quality


La importancia de los modelos y procedimientos para la planificación, seguimiento y control en la...

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