Workshop on “Monitoring Quality of
Service and Quality of Experience of Multimedia
Services in Broadband/Internet Networks”
(Maputo, Mozambique, 14-16 April 2014)
Key QoS parameters for Voice
Services
Martin Brand
Vice Chair ITU-T Study Group 11
Joachim Pomy
Consultant@joachimpomy.de
OPTICOM, Germany
Components and related QoS category with
voice quality functions

Maputo - Mozambique - 14 - 16 April 2013
2
ITU-T G.114
ITU-T G.107
 Highly interactive tasks (e.g.,
 Absolute delay does not
some speech, video
conferencing and interactive data
applications) may be affected by
delays below 100 ms.
 For many intra-regional (e.g.,
within Africa, Europe, North
America) routes in the range of
5000 km or less, users of VoIP
connections are likely to
experience mouth-to-ear delays
< 150 ms.
impair the intelligibility of
speech but if the total delay
exceeds around 100 ms from
mouth to ear, it begins to affect
the interactivity of
conversations. Therefore, if
possible, large delays should be
avoided.
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4
Contributing Factors
Delay
-
Codec
Packet frame duration
DSP/CPU processing time
Play out buffer
Link speed (serialization)
Propagation delay
De-jitter buffer delay
PLC
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Distorsion
- Codec
-
Jitter
Use of VAD
Lost of packets
Transcoding
Sound level
Echo level
5
E-Model Transmission Rating (R)
ITU-T Rec. G.107
 R summarizes the effects of network impairments including delay,
distortions signal level & echo level
R= Ro- Is - Id- Ie + A
Simplified E-Model for codec and packet loss/burst impairments R =
93.4 – Ie
Ro= basic signal to noise ratio
Is= level impairments and distortion impairments
Id= delay impairments
Ie= codec and packet loss/burst impairments
A= advantage factor
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6
Provisional planning values for the equipment
impairment factor (Ie)
Codec type
Reference
Operating rate kbit/s
Ie value
G.726, G.727
40
2
G.721(1988), G.726, G.727
32
7
G.726, G.727
24
25
G.726, G.727
16
50
G.728
16
7
12.8
20
G.729
8
10
G.729-A  VAD
8
11
VSELP
IS-54
8
20
ACELP
IS-641
7.4
10
QCELP
IS-96-A
8
19
RCELP
IS-127
8
6
VSELP
Japanese PDC
6.7
24
RPE-LTP
GSM 06.10, Full-rate
13
20
VSELP
GSM 06.20, Half-rate
5.6
23
ACELP
GSM 06.60, Enhanced Full Rate
12.2
5
ACELP
G.723.1
5.3
19
MP-MLQ
G.723.1
6.3
15
ADPCM
LD-CELP
CS-ACELP
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Codec combination
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8
E-Model Prediction of Echo and Delay
Impairment
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Relation between R-value and user satisfaction
R Value
MOS CQEN
Categories of User Satisfaction
Value
94
4,42
93
4,40
92
4,38
Very satisfied (Best)
91
4,36
90
4,34
87
4,195
85
4,18
82
4,09
81
4,06
Satisfied (High)
80
4,03
77
3,85
73
3,74
70
3,60
Some users dissatisfied (Medium)
68
3,50
60
3,10
Many users dissatisfied (Low)
50
2,58
Nearly all users dissatisfied (Poor)
MOS = 1 + (0,035) × R + (000 007) × R (R - 60) (100 - R)
NOTE 1: Connections with R-values below 50 are not recommended.
NOTE 2: Although the trend in transmission planning is to use R-values,
equations to convert R-values into other metrics e.g. MOS, % GoB, %
PoW, can be found in ITU-T Recommendation G.107 [i.4], annex B.
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Provisional Planning Values for the Equipment
Impairment Factor Ie under Conditions of Packet Loss
for Codecs G.711, G.729A + VAD and G.732.1 + VAD
60
50
40
Ie 30
20
10
0
0
5
10
15
20
25
Packet Loss %
G.711 without PLC
G.711 with PLC Bursty Packet Loss
G.723.1 + VAD
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G.711 with PLC Random Packet Loss
G.729A + VAD
GSM 06.60 EFR
11
MOS - Speech Quality Measure
5
Excellent

Subjective measurement
 Based on subjective experiments
 Mean opinion score
 Costly and time consuming

Objective measurement
 Good correlation with subjective
measurement
 Highly repeatable
 Real-time
4
Good
3
Fair
2
Poor
MOS
1
Bad
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QoS Voice Testing (1)
 Active voice quality measurement
 Active voice quality measurement techniques, also known as
intrusive models, require a test call to be made over the network. A
comparison of reference and degraded signals produces a quality
score based on MOS. This type of measurement is useful for the
preinstallation testing of a system as well as network optimization.
 Passive voice quality measurement
 Common to all communication technologies are Passive voice
quality measurement. Passive voice quality measurement is also
known as a non-intrusive measurement.
 These models monitor live network traffic and again measure the
voice quality on the MOS scale. Passive measurement is ideal for
the testing of systems already in use
13
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QoS Voice Testing (2)
 PSQM ITU-T Rec. P.861 - designed for codec evaluation.
Assesses error loudness, noise disturbance and asymmetry to predict a PSQM value
Withdrawn February 2001
 PAMS - developed for real world networks
Assesses time aligned, level aligned, spectrally weighted error surface
 PESQ© - ITU-T Rec. P.862 Perceptual Evaluation of Speech
Quality
Designed for network avaluation, using specific scale
 PESQ© - ITU-T Rec. P862.1 (PESQ extension from
Nov.2003)
Linear mapping to P.800 MOS scale
14
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QoS Voice Testing (3)
 PESQ© - ITU-T Rec. P862.3 [2007] (Implementation guide,
Methods for objective and subjective assessment of quality)
 POLQA – ITU-T Rec. P.863 [2011]
 3SQM, perceptual single-sided speech quality measure
(non-intrusive) according to ITU-T rec. P.563 [2004]
15
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The instance of media-information quality
assessment methods comparison
Accuracy
High
Good
Average
Method type
High
PESQ, POLQA


Active
Average

P.563

Passive
Low


E-model
Cost
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Passive/
Modelling
16
GUIDANCE ON OBJECTIVES FOR QUALITY
RELATED PARAMETERS AT VOIP SEGMENTCONNECTION POINTS
RESULTS PUBLISHED IN
ETSI TR 102 775 V.1.6.1
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Scope of the development
To provide guidance on the quality
parameters that need to be considered at the
Segment-connection of Voice over IP (VoIP)
services and provides guidance on objectives
for these parameters.
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Reference Configuration
NGN
Provider A
NGN
Provider C
Total transit segment
Regional
Metro
Transit
Segment
A1
Transit
Segment
C1
NNI
NNI
Regional
Access
Segment A
Transit
Segment
B1
Access
Segment C
NGN Provider B
UNI
UNI
CPN
User
Segment A
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CPN
User
Segment C
19
Generic Segment-connection Points
QoS View
Iz/Ic
CPN
Iz/Ic
IP Transit
SBC
UNI
Access Network
CPN
SBC
SBC
NGN
Interconnection Server
or
Transit Network
SBC
NGN
UNI
Access Network
UNI-UNI
NGN Functional Archutecture View
Non-compatible
Control domain
IWF
Ic
Iw
Service Control
Subsystem
Compatible
Control domain
Service Layer
Transport Layer
RACS
Iz
Iz
I-BGF
SoIx interconnection reference model
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End-to-End delay values between originating and terminating
Service Provider premises
West
Europe
Vienna
West Europe
Bern
Paris
Frankfurt
DE - AT
(Frankfurt –
Vienna)
7 ms
CH – DE
(Bern –
Frankfurt)
8 ms
CH - AT
(Bern –
Vienna)
10 ms
FR- AT
(Paris -.
Vienna)
15 ms
North Europe
East Europe
RU – Vladimir
RU – Moskwa
SE - Östersund
RO – Bucharest
HU – Budapest
CH - RU
(Bern – Vladimir)
23 ms
CH - RU
(Bern – Moskwa)
22 ms
CH-RO
CH-GR
(Bern – Bucharest) (Bern –
25 ms
Athens)
30 ms
DE-RO
(Frankfurt –
DE-GR
Bucharest)
(Frankfurt –
18 ms
Athens)
24 ms
DE-HU
(Frankfurt –
IT-CH
Budapest)
(Roma –
12 ms
Cern)
22 ms
DE- RU
(FrankfurtMoskwa)
21 ms
DE-SE
(Frankfurt –
Östersund)
12 ms
South
Europe
GR–Athens
IT - Roma
East Asia
South Asia
Oceania
(CNDongguan)
Malaysia - MY
Australia -AU
Sydney
CH – CN
(Bern(Dongguan)
150 ms
CH- MY
110 ms
DE – MY
115- 164 ms
DE-CN
(Frakfurt –
Dongguan)
160 ms
DE-AU
(Frankfurt –
Melburne)
165 ms
N. America
West Cost
Central America
South America
Africa
US
Washington
DC
US
Vancouver
Panama - PA
Mexiko- MEX
Brasilia - BR
ZA - Cap town
CH- US
(Bern –
Washington)
46 ms
CH-US
(Bern –
Vancouver)
75 ms
CH-PA
(Bern –
Panama)
103 ms
CH-BR
(Bern – Sao
Paulo)
136 ms
CH-ZA
(Bern - Cape
Town)
108 ms
DE-US
(Frankfurt –
Washington)
55 ms
DE-US
(Frankfurt –
Vancouver)
75 ms
DE-MEX
(Frankfurt –
Mexiko City)
75 ms
DE-BR
DE-ZA
(Frankfurt –
Cape Town)
90 ms
Burkina Fasso
DE-AU
(Frankfurt –
Sydney)
146 ms
(Frankfurt –
Sao Paulo)
125 ms
BE-BF
90 – 130 ms
North
Europe
(SEÖstersund)
SE - RU
(Östersund –
Moskwa)
10 ms
SE-RO
(Östersund –
Bucharest)
30 ms
Frankfurt –
Roma
13 ms
SE-GR
(ÖstersundAthens)
42 ms
East Europe
(HUBudapest)
HU- RU
(Budapest –
Moskwa)
33 ms
HU – RO
(BudapestBucharest)
14 ms
HU – GR
HU-CN
(Budapest – 166 ms
Athens)
20 ms
HU-MY
125 ms
IT- RU
(Roma –
Moskwa)
38 ms
IT-RO
(Roma –
Bucharest)
32 ms
(IT-GR)
Roma –
Athens
23 ms
IT-MY
150 ms
South
Europe
(IT- Roma)
CH-AU
(Bern – Sydney)
170 ms
N. America
East Cost
SE-CN
150 ms
IT-CN
160 ms
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SE-MY
124 ms
SE-AU
171 ms
HU-AU
170 ms
IT-AU
160 ms
SE-US
62 ms
HU-US
60 ms
IT-US
55 ms
SE-US
83 ms
SE- PA
84 ms
SE-BR
155 ms
SE-ZA
87 ms
HU-US
100 ms
SE-MEX
78 ms
HU-PA
95 ms
HU-BR
152 ms
HU-ZA
100 ms
IT-US
95 ms
HU- MEX
96 ms
IT – PA
104 ms
IR-BR
108 ms
IT-ZA
95 ms
IT- MEX
113 ms
21
Reference Configurations (1)
SBC
ADM
DL
CL
SBC
IP Transit
SBC
CL
DL
ADM
SBC
Backbone
TE
TE
Local
exchange
Transit
exchange
EC
SBC
MGW
VoNGN
PSTN
PSTN/ISDN classic access Configuration
TE
TE
Subscriber line
digital junction
EC
MSAN
(MGW)
SBC
VoNGN
PSTN
NGN PSTN/ISDN access Configuration
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ADM
DL
CL
TRAU
ETH
Add-Drop-Multiplexer
router Distribution Layer
router Core Layer
Transcoder and Rate Adaption
Ethernet Unit
22
Reference Configurations (2)
TE
TE
IAD
DSLAM
ETH
2X
ADM
4x
BRAS /
BNG
SBC
VoNGN
PSTN
Access DSL Configuration
Node
B
ATM RNC
ATM
TRAU
MGW
SBC
VoNGN
Access configuration from UMTS Release 4
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23
Delay with regional propagation delay (1 400 km / 7 ms)
Uplink /
Downlink
POTS
256
kbit/s
-
256 kbit/s
128 ms
R=90
384 kbit/s
-
384
kbit/s
-
512
kbit/s
-
768
kbit/s
-
118 ms 113 ms 108 ms
R=90
R=90
108 ms 102 ms
R=90
R=91
1024
kbit/s
-
1152
kbit/s
-
1536
kbit/s
-
2048
kbit/s
-
2304
kbit/s
-
3072
kbit/s
-
6144
kbit/s
-
POTS
55 ms
104 ms
103 ms
102 ms
101 ms
101 ms
100 ms
97 ms
R=91
82 ms
R=91
R=911
R=91
R=91
R=91
R=91
R=91
R=90
R=90
97 ms
95 ms
93 ms
94 ms
92 ms
92 ms
91 ms
91 ms
75 ms
R=91
R=91
R=91
R=91
R=80
R=91
R=91
R=91
R=91
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Delay with regional propagation delay (1 400 km / 7 ms)
G.711/20
Uplink /
Downlink
256
kbit/s
-
384
kbit/s
-
512 kbit/s
768 kbit/s
Uplink /
Downlink
1024 kbit/s
POTS
256 kbit/s
2048 kbit/s
384 kbit/s
GSM
768
kbit/s
92 ms
1024
kbit/s
91 ms
1152
kbit/s
91 ms
1536
kbit/s
91 ms
2048
kbit/s
91 ms
2304
kbit/s
90 ms
3072
kbit/s
90 ms
6144
kbit/s
90 ms
74 ms
R=91
R=91
R=91
R=91
R=91
R=91
R=91
R=91
R=91
R=91
90 ms
90 ms
90 ms
89 ms
89 ms
89 ms
89 ms
73 ms
-
-
-
91 ms
256
kbit/s
--
384
kbit/s
--
512
kbit/s
--
R=91
kbit/s
--
R=91
kbit/s
90 -ms
R=91
R=91
R=91
R=91
128 ms
118 ms
113 ms
108 ms
104 ms
103 ms
102 ms
101 ms
R=90
-
R=90
-
R=90
-
R=90
-
R=90
-
R=911
-
88 ms
R=91
88 ms
R=91
-
108 ms
102 ms
97 ms
95 ms
93 ms
94 ms
R=91
92 ms
R=90
R=91
R=91
R=91
R=91
R=91
196
ms
194ms
193
ms
193 ms
192 ms
R=82
R=82
202 ms
R=81
UMTS Rel.4
512
kbit/s
97 ms
207 ms
768
R=82
R=81
201
ms
199
ms
R=82
198
ms
R=81
157
ms
R=81
155
ms
R=81
154
ms
R=80
LTE
163ms
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1024
-
1152
R=91
kbit/s
89 -ms
R=91
1536
R=91
kbit/s
89 -ms
2048
R=91
kbit/s
89 -ms
2304
R=91
kbit/s
89 -ms
3072
6144
POTS
POTS
R=91
kbit/s
88 -ms
R=91
kbit/s
88 -ms
R=91
73
55 ms
ms
R=91
R=91
R=91
R=91
R=91
101 ms
100 ms
97 ms
82 ms
88 ms
R=91
88 ms
R=91
88 ms
R=91
92 ms
R=91
91 ms
R=91
91 ms
R=91
75 ms
R=80
R=91
R=91
R=91
R=91
192 ms
192 ms
192 ms
191 ms
191 ms
175
ms
R=82
R=82
R=82
R=82
R=82
198 ms
197 ms
197 ms
197 ms
197 ms
196 ms
196 ms
R=81
R=81
R=81
R=81
R=81
R=81
R=81
154 ms
154 ms
153 ms
153 ms
153 ms
152 ms
152 ms
R=91
R=83
180
ms
R=82
136
ms
25
Relation between R-value and user satisfaction
R Value
MOS CQEN
Categories of User Satisfaction
Value
94
4,42
93
4,40
92
4,38
Very satisfied (Best)
91
4,36
90
4,34
87
4,195
85
4,18
82
4,09
81
4,06
Satisfied (High)
80
4,03
77
3,85
73
3,74
70
3,60
Some users dissatisfied (Medium)
68
3,50
60
3,10
Many users dissatisfied (Low)
50
2,58
Nearly all users dissatisfied (Poor)
MOS = 1 + (0,035) × R + (000 007) × R (R - 60) (100 - R)
NOTE 1: Connections with R-values below 50 are not recommended.
NOTE 2: Although the trend in transmission planning is to use R-values,
equations to convert R-values into other metrics e.g. MOS, % GoB, %
PoW, can be found in ITU-T Recommendation G.107 [i.4], annex B.
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26
Guidance on Access Segment Objectives
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27
Maximal IPDV values for xDSL and ETH Access
Segment
Parameter
Value
Access Network (sending side)
< 35 ms
Access Network (receiving
< 10 ms (note)
side);
NOTE: 10 ms are recommended, the maximum
IPDV value is 40 ms.
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Guidance on Objectives for Total
Transit Segments
Parameter
Value
IPDV
10 ms
Intra-continent Jitter Value -5 ms per Provider
(maximum of 2 involved in the service delivery
chain) (see note)
IPDV
20 ms
Inter-continent Jitter Value -10 ms per Provider
(maximum of 2 involved in the service delivery
chain) (see note)
IPLR
3,0 × 10-4
IPER
3 × 10-5
Ie
0
NOTE: The Jitter Values are based on values contained in the
GSMA document IR.3445 [i.15].
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29
Dependence of DSP/CPU processing time
TriplePlay-Results IAD_2_IAD
Test requerments : routed IAD-Konfiguration,
worst case
two TV Streams,
Testlabor HSI- Connection and activated WLAN, VP-voice
upstream Bandwith 384 kBit/s.
Supplier:
1
2
3
4
IAD_2_IAD MOS Value
QoS two wire (PSTN)
10 ms packetization
20 ms packetization
4,2
4,2
4,2
4,2
4,0
4,0
4,2
4,1
10 ms packetization
58/29/10
20 ms packetization
66/35/11
86/10/4
95/0/0
111/10/4
114/13/6
63/17/6
66/10/4
Delay / Delay Range/ Std-Dev
(each direction max values)
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30
Delay Objectives for BEST (G.109) voice communication
quality (R > 90) and Access Network Jitter < 35 ms
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31
Bandwidth calculations and prioritization in VoIP
systems
The IP delay of VoIP packets over a link transporting Voice and Data
depends on following factors:
• the instantaneous system load (not the average system load),
• the size of the packets (both the size of the RTP packets and IP
data packets on the same links),
• the manner in which QoS is implemented in the system (a
system with priority, such as Diff-Serv, behaves differently than a
system with best effort).
The delay and jitter increase linearly up to a limit of parallel VoIP
channels. Above this limit, the bandwidth utilization and the delay
increase exponentially and the VoIP transmissions become unstable.
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33
RTP is transferred preferentially
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34
The maximum link capacity
The maximum capacity with Diff-Serv is bandwidth dependent. For example,
the utilization for a 386 kbit / s link should not be higher than 85%, a 4 Mbit/s
link can be utilized with 96 %.
Utilization (ρ1+ ρ2)
RHO < 0.96
RHO < 0,95
RHO < 0,89
RHO < 0,89
RHO < 0,85
Tests conditions:
Link capacity
> 4 Mbit/s
3 Mbit/s
2 - 3 Mbit/s
1 - 2 Mbit/s
0,386 - 1 Mbit/s
Data utilization ρ2= 62 %;
Data Packet size = 1500 bytes;
Codec: G.711
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35
QoS is implemented by over-dimensioning of the
system
Without prioritization only 40 % to 80% of the bandwidth can be used depending
on the flow characteristics, as can be seen in the following figure:
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36
Any questions
?
Contact:
Consultant@joachimpomy.de
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37