Wireless Access Research Adil Raja August 2007 A Methodology for Deriving VoIP Equipment Impairment Factors for a Mixed NB/WB Context Adil Raja 13 th August, 2007
Jun 09, 2015
Wireless Access Research
Adil Raja August 2007
A Methodology for Deriving VoIP Equipment Impairment Factors for a
Mixed NB/WB Context
Adil Raja
13th August, 2007
Wireless Access Research
Adil Raja August 2007
VoIP- The Shift to WB Paradigm
• The NB and WB would have to coexist for some time. i.e. operate either in cascade or in parallel.
• This work proposes an extension to E-Model for the parallel case.
Wireless Access Research
Adil Raja August 2007
The E-Model
• An Instrumental Model initially designed for NB handset telephony.
• R= R0-Is-Id-Ie,eff+A• R0=93.2 – the basic SNR.• Is - simultaneous impairments e.g. OLR, non-
optimum sidetone.• Id - e.g e2e delay and echo.• Ie,eff Impairments due to low-bitrate codecs and
packet loss.• A – Advantage factor.
Wireless Access Research
Adil Raja August 2007
The E-Model…
• R <-> MOS
Wireless Access Research
Adil Raja August 2007
Moller’s WB extension to E-Model
• Consider Two experiments• Each experiment is composed of two sets of speech
samples.• MOS evaluation is done based on ACR paradigm.• One set is evaluated in the NB/WB context.• The other set is evaluated in the NB context, by
downsampling the WB coded speech samples.
Wireless Access Research
Adil Raja August 2007
ExampleSpeech quality evaluation on narrowband
conditions only
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Su
bje
ctiv
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OS
C1 C2
C3 C4
C5 C6
C7 C8
C9 C10
C11 C12
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C15 C16
C17 C18
C19 C20
C21 Reference
Speech quality evaluation for narrowband and wideband conditions
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Su
bje
cti
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MO
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C1 C2
C3 C4
C5 C6
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C9 C10
C11 C12
C13 C14
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C21 Reference
Wireless Access Research
Adil Raja August 2007
ExampleRelationship between MOS for narrowband conditions
and MOS for wideband conditions
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Subjective NMOS
Su
bje
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MM
OS
STUDY GROUP 12 – DELAYED CONTRIBUTION 46
Discussion on unified objective methodologies for the comparison of voice quality of narrowband and wideband scenarios
Wireless Access Research
Adil Raja August 2007
The Extension
• Rnb=a+(eRnb/wb/b-1)
• a=169.38
• b=176.32
• The R-scale is stretched by 29%
• A linear extension with somewhat similar results exists.
Wireless Access Research
Adil Raja August 2007
R-scale extension with PESQ
• Two sets of speech samples are created.
• Both contain stimuli coded by NB and WB codecs. (124 samples each).
• The first (NB/WB) set is evaluated using PESQ-WB.
• The NB coded stimuli were upsampled to 16 kHz.
Wireless Access Research
Adil Raja August 2007
R-scale extension with PESQ
• How to evaluate the 2nd part of the test?
• For the 2nd (NB) part of test three options were considered for evaluating the samples.
• In Option 1 All the files (ref|deg of NB|WB) were downsampled to 8 kHz.
• This qualifies as a NB test.
Wireless Access Research
Adil Raja August 2007
R-scale extension … Option 1
RNB=a+b*RNB/WB
Max RNB=100.48
Suggests no extension.
Wireless Access Research
Adil Raja August 2007
The outcome
Wireless Access Research
Adil Raja August 2007
R-scale extension … Option 2
All Evaluation is done by PESQ-WB.
Contracts the scale instead.
Wireless Access Research
Adil Raja August 2007
R-scale extension … Option 3
• Same as Option 2 but the Ref samples for NB stimuli are downsampled/upsampled.
• This would clearly tantamount to repeating option 1 but with PESQ-WB
Wireless Access Research
Adil Raja August 2007
An Alternative
Using Supp 23 Exp 1&3.
Mapping between PESQ-WB & -NB evaluted NB coded samples.
Max RNB=107.1786
Wireless Access Research
Adil Raja August 2007
The Codecs
• G.729
• AMR-NB – 7.4 & 12.2 kbps
• G.723.1 – 6.3 kbps
• G.722.1 24/32 kbps
• G.722.2 – all 9 modes
Wireless Access Research
Adil Raja August 2007
Other metrics
• MLR - [0,2.5,. . . , 15, 20, . . . , 40]%• CLP - 10, 50, 60, 70 and 80%. • PI – 10-60 ms.• A total of 2,820 conditions were simulated• A given condition was applied to a file for 30 times; to
negate the effect of loss location.• Thus a total of 3,38,400 speech files were created.• Evaluation was done on beowulf using PESQ-WB
Wireless Access Research
Adil Raja August 2007
Ie,wb,eff vs various codecs
Wireless Access Research
Adil Raja August 2007
Scatter plot –training data
Wireless Access Research
Adil Raja August 2007
Scatter plot-Testing data
Wireless Access Research
Adil Raja August 2007
Surface plots of the derived functions
Wireless Access Research
Adil Raja August 2007
Parameter Significance
Wireless Access Research
Adil Raja August 2007
Ie,wb,eff vs mlr and mbl
Wireless Access Research
Adil Raja August 2007
Ie,wb,eff vs mlr and PI