colombia, 23-24 september 2013 the importance of models and procedures for planning, monitoring and...
TRANSCRIPT
Colombia, 23-24 September 2013
The importance of models and procedures The importance of models and procedures for planning, monitoring and control in the for planning, monitoring and control in the
provision of communications servicesprovision of communications services
Dr.-Ing. H. W. GierlichHead 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)
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Outline
IntroductionCommunication Services – Underlying System configurations Planning: The ITU-T E-model (G.107 & G.108)Network Monitoring: P.862, P.863 & P.563Wideband – The new ChallengeSummary
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.
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Speech Quality – what we would like to have
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1m
““orthotelefonic reference position”orthotelefonic reference position”
Speech Quality…
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speechquality
talkingsituation
listeningsituation
conversationalsituation
… from the user’s perspective
End to End Conifguration
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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 !add. 1 - 100 ms !
Netw. 2
Impact on speech quality: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 :
delaydelay – unpredictable, load dependant, time variant
Contributions to Quality
The networksType of networksInterconnectionQoS management
The endpointsTypes of terminalsInteroperability
Terminal – NetworkTerminal – Terminal
The users‘ locationEnvironmental conditions
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• Network planningNetwork planning
• Network monitoringNetwork monitoring
• Laboratory Laboratory terminal testingterminal testing
• Interoperability Interoperability testing testing
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Outline
IntroductionCommunication Services – Underlying System configurations Planning: The ITU-T E-model (G.107 & G.108)Network Monitoring: P.862, P.863 & P.563Wideband – The new ChallengeSummary
Reference Connection in the E-model
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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)
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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 Impairment factorsfactors
Simultaneous impairment factor Is Is (non optimum loudness rating, non optimum sidetone, PCM coding distortion)
Delayed impairment factor Id Id (impact of delay, talker- or listener echo)
Equipment impairment factor Ie Ie (all types of impairments in equipment such as coding distortion including the effect of packet loss)
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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.113From subjective listening tests described in ITU-T P.833From objective models (e.g. ITU-T P.863) following the procedure in ITU-T P. 834
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Some Ie factors from G.113
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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:
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1000 R
1MOSCQE
6CQE
107)100)(60(035.01MOS RRRR
5.4MOSCQE
Guide for User Satisfaction based on R-values
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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
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Outline
IntroductionCommunication Services – Underlying System configurations Planning: The ITU-T E-model (G.107 & G.108)Network Monitoring: P.862, P.863 & P.563Wideband – The new ChallengeSummary
Networks & Network Monitoring
Main network related impairments:DelayDelay variation (jitter)Listening speech impairment due to
CodingTranscodingInterconnection Packet loss/jitter
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ITU-T Models for Perceptual based Speech Quality Measurement
ITU-T P.862 (2001): PESQITU-T P.863 (2011): POLQAThe basic principle:
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Principle
Intrusive test procedureObjective prediction of MOS (mean opinion score) as achieved in listening test subjectively Prediction on a MOS-scale:
MOS 5 – excellentMOS 4 – goodMOS 3 – fairMOS 2 – poorMOS 1 – bad
Substitution of subjective tests for known codecs and impairments
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Application
Intrusive testing:Insertion of a reference speech sequenceAcquiring the transmitted, distorted speech sequenceCalculation of the speech quality by comparing to the referenceOutput: MOS LQOn – MOS LQOn – mean opinion score, objective, narrowband
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Typical setups
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Central server- automated call setup-generation of test sequences- analysis & statistics
FixedNetwork
FixedNetwork
Probe @ NTP- automated call setup-generation of test sequences
Probe @ NTP- automated call setup-generation of test sequences
Mobile Network
Mobile Network
Mobile Probe - automated call setup-generation of test sequences
Mobile Probe - automated call setup-generation of test sequences
FixedNetwork 2
FixedNetwork 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 callNo reference file insertion requiredAverage listening speech quality prediction on statistical evaluation of a high number of calls on the same connectionNot recommended for test on a call by call basisMuch less reliable than intrusive testing based on P.862 and P.863
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The wideband challenge
High quality expectation by the userWideband must be significantly better in all quality aspectsSignificant contribution to quality by the terminalsFirst attemt to certify high quality wideband speech transmission: GSMA
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Wideband listening examples
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(.wav)
Fullband
Narrowband
Wideband
Mobile Phone
Mobile signal
processingRF-Interface
air interface
SpeechTranscoder
speechspeechnoisenoise
Wideband (.wav)
Narrowband (.wav)……in noisein noise
Wideband Network Planning – ITU-T G.107.1
The principle of the model is identical to the narrowband version G.107The 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 0-100All factors – R0 and Impairment factors are adapted accordingly
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Wideband Network Monitoring
Setup as in narrowbandOnly intrusive testing available Network monitoring is based on ITU-T P.863 POLQAITU-T P.862 PESQ should not be used in wideband
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Conclusions and Recommendations
ITU-T provides models for planning and monitoringNetwork planning is essential for achieving high network QoSNetwork 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
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