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Wireless Access ResearchAdil Raja August 2007
A Methodology for Deriving VoIP Equipment Impairment Factors for a
Mixed NB/WB Context
Adil Raja13th August, 2007
Wednesday 14 November 2012
Wireless Access ResearchAdil 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.
Wednesday 14 November 2012
Wireless Access ResearchAdil 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.
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
The E-Model…
• R <-> MOS
Wednesday 14 November 2012
Wireless Access ResearchAdil 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.
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
Example
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
ExampleSTUDY GROUP 12 – DELAYED CONTRIBUTION 46
Discussion on unified objective methodologies for the comparison of voice quality of narrowband and wideband scenarios
Wednesday 14 November 2012
Wireless Access ResearchAdil 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.
Wednesday 14 November 2012
Wireless Access ResearchAdil 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.
Wednesday 14 November 2012
Wireless Access ResearchAdil 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.
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
R-scale extension … Option 1RNB=a+b*RNB/WB
Max RNB=100.48
Suggests no extension.
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
The outcome
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
R-scale extension … Option 2
All Evaluation is done by PESQ-WB.
Contracts the scale instead.
Wednesday 14 November 2012
Wireless Access ResearchAdil 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
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
An AlternativeUsing Supp 23 Exp 1&3.
Mapping between PESQ-WB & -NB evaluted NB coded samples.
Max RNB=107.1786
Wednesday 14 November 2012
Wireless Access ResearchAdil 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
Wednesday 14 November 2012
Wireless Access ResearchAdil 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
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
Ie,wb,eff vs various codecs
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
Scatter plot –training data
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
Scatter plot-Testing data
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
Surface plots of the derived functions
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
Parameter Significance
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
Ie,wb,eff vs mlr and mbl
Wednesday 14 November 2012
Wireless Access ResearchAdil Raja August 2007
Ie,wb,eff vs mlr and PI
Wednesday 14 November 2012