ETSI TR 103 138 V1.2.1 (2014-11)

Speech and multimedia Transmission Quality (STQ); Speech samples and their use for QoS testing

RTR/STQ-00202m

General Information

• Status: Published
• Publication Date: 17-Nov-2014
• Technical Committee: STQ MOBILE - STQ Mobile
• Current Stage: 12 - Completion
• Due Date: 10-Dec-2014
• Completion Date: 18-Nov-2014

Standards Content (Sample)

ETSI TR 103 138 V1.2.1 (2014-11)






TECHNICAL REPORT
Speech and multimedia Transmission Quality (STQ);
Speech samples and their use for QoS testing

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2 ETSI TR 103 138 V1.2.1 (2014-11)



Reference
RTR/STQ-00202m
Keywords
QoS, quality, speech
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3 ETSI TR 103 138 V1.2.1 (2014-11)
Contents
Intellectual Property Rights . 4
Foreword . 4
Modal verbs terminology . 4
Introduction . 4
1 Scope . 5
2 References . 5
2.1 Normative references . 5
2.2 Informative references . 5
3 Abbreviations . 6
4 Devices and network access . 6
4.1 Mobile devices . 6
4.2 ISDN/PSTN . 7
4.3 Narrowband and wideband scenarios . 7
4.3.1 Narrowband telephony and narrowband test scenario . 7
4.3.2 Wideband telephony and super-wideband test scenario . 8
5 Speech samples . 9
5.1 Pre-filtering of speech signals . 9
5.1.1 Filter for narrow-band test scenarios . 9
5.1.1.1 IRS send Filter . 9
5.1.1.2 MSIN Filter . 10
5.1.1.3 Recommended filters to use in narrowband mobile test scenarios . 11
5.1.2 Filter for wideband telephony test scenarios . 11
5.1.2.1 14 kHz bandpass . 11
5.1.2.2 Recommendation ITU-T P.341 . 11
5.1.2.3 Recommended filters to use in super-wideband mobile test scenarios . 11
5.1.3 Reference signals . 12
5.2 Audio level . 12
5.2.1 Nominal level . 12
5.2.2 Level adjustment with Recommendation ITU-T P.56 . 12
5.2.3 Input level at test devices . 12
6 Scenarios . 13
6.1 Narrowband-Measurement Land to Mobile . 13
6.2 Narrowband-Measurement Mobile to Land . 13
6.3 Mobile to Mobile . 13
6.3.1 Narrowband . 14
6.3.2 Wideband . 14
7 Synopsis . 15
Annex A: Coefficients for the reconstruction lowpass filter . 16
Annex B: Bibliography . 17
Annex C: Speech Samples . 18
C.1 Introduction . 18
History . 19

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4 ETSI TR 103 138 V1.2.1 (2014-11)
Intellectual Property Rights
IPRs essential or potentially essential to the present document may have been declared to ETSI. The information
pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found
in ETSI SR 000 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in
respect of ETSI standards", which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web
server (http://ipr.etsi.org).
Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee
can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web
server) which are, or may be, or may become, essential to the present document.
Foreword
This Technical Report (TR) has been produced by ETSI Technical Committee Speech and multimedia Transmission
Quality (STQ).
Modal verbs terminology
In the present document "shall", "shall not", "should", "should not", "may", "may not", "need", "need not", "will",
"will not", "can" and "cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms
for the expression of provisions).
"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.
Introduction
Conducting drive test in multi technology environment presents a challenge to all parties. And the complexity and
variance of the different scenarios need to be broken down to handy instructions for those who actually configure and
conduct the measurements, such as Network Operators, Service Providers, Equipment Vendors and Regulatory
Authorities.
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5 ETSI TR 103 138 V1.2.1 (2014-11)
1 Scope
The present document introduces and explains the use and application of speech samples to determine the objective
listening quality (LQO) in narrowband (NB), wideband (WB) and super-wideband (SWB) for different scenarios such
as connections between fixed networks and mobile terminals.
2 References
References are either specific (identified by date of publication and/or edition number or version number) or
non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the
referenced document (including any amendments) applies.
Referenced documents which are not found to be publicly available in the expected location might be found at
http://docbox.etsi.org/Reference.
NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee
their long term validity.
2.1 Normative references
The following referenced documents are necessary for the application of the present document.
Not applicable.
2.2 Informative references
The following referenced documents are not necessary for the application of the present document but they assist the
user with regard to a particular subject area.
[i.1] Recommendation ITU-T P.48: "Specification for an intermediate reference system".
[i.2] Recommendation ITU-T P.800: "Methods for subjective determination of transmission quality".
[i.3] Recommendation ITU-T P.830: "Subjective performance assessment of telephone-band and
wideband digital codecs".
[i.4] Recommendation ITU-T P.862: "Perceptual evaluation of speech quality (PESQ): An objective
method for end-to-end speech quality assessment of narrow-band telephone networks and speech
codecs".
[i.5] Recommendation ITU-T P.862.1: "Mapping function for transforming P.862 raw result scores to
MOS-LQO".
[i.6] Recommendation ITU-T P.862.2: "Wideband extension to Recommendation P.862 for the
assessment of wideband telephone networks and speech codecs".
[i.7] Recommendation ITU-T P.862.3: "Application guide for objective quality measurement based on
Recommendations P.862, P.862.1 and P.862.2".
[i.8] Recommendation ITU-T P.863: "Perceptual objective listening quality assessment (POLQA)".
[i.9] Recommendation ITU-T P.863.1: "Application Guide for the Recommendation ITU-T P.863".
[i.10] Recommendation ITU-T G.711: "Pulse code modulation (PCM) of voice frequencies".
[i.11] Recommendation ITU-T G.191: "Software tools for speech and audio coding standardization".
[i.12] Recommendation ITU-T P.341: "Transmission characteristics for wideband digital loudspeaking
and hands-free telephony terminals".
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[i.13] Recommendation ITU-T P.56: "Objective measurement of active speech level".
3 Abbreviations
For the purposes of the present document, the following abbreviations apply.
AMR Adaptive Multi-Rate codec
AMR-WB Adaptive Multi-Rate codec Wide Band
ASL Active Speech Level
EFR Enhance Full Rate codec
FIR Finite Impulse Response filter
IRS Intermediate Reference System
ISDN Integrated Services Digital Network
LQO Listening Quality Objective
MOS Mean Opinion Score
MSIN Mobile Station Input filter
NB Narrow Band
NTP Network Terminating Point
OVL Overload point
PBX Private Branch Exchange
PC Personal Computer
PCM Pulse Code Modulation
PSTN Public Switch Telecommunication Network
SWB Super Wide Band
WB Wide Band
4 Devices and network access
There are only a few devices and access interfaces that play a role in end-to-end mobile network testing. In end-to-end
testing a test connection between two endpoints is established. This determines the access interfaces and devices.
4.1 Mobile devices
The mobile device is not a pure access device to the mobile network. It contains complex components for speech
processing and becomes therefore an important contributor to the overall quality measured in the test connection.
Mobile devices do not have a standardized audio interface, neither digital nor analogue. As common practice the
headset connector of the mobile device is used as access interface for audio insertion and capturing. As a pre-condition
for audio insertion and capturing, the measurement equipment has to match to the devices headset connector in
impedance and level.
It has to be noted that in this setup the mobile devices are used in headset mode. Devices apply individual audio
profiles, means individual settings in filtering, amplification and noise- and echo treatment for connected headphones or
the use of the internal microphone. Often there is a third mode that applies when a handsfree loudspeaker set is
connected. Since the audio processing in headphone mode is different from the use of internal microphone, such a test
connection emulates a user with a headphone (personal handsfree kit) connected by wire to the headphone connector.
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7 ETSI TR 103 138 V1.2.1 (2014-11)
4.2 ISDN/PSTN
ISDN or (analogue) PSTN interfaces are not directly belonging to the mobile network but they are usually used as
defined endpoint of the test connection. As access point to the ISDN or PSTN network a real consumer telephone
device is not used but rather an ISDN or PSTN interface module as e.g. a PC card. It enables an electrical connection to
the network for audio transmission and processes all the signalling information. The interface module or PC card is
usually accessed with a digitalized speech signal in PCM format. The format is preferably 16 bit or 13 bit linear PCM
sampled at 8 kHz or 16 kHz. Some interfaces expect 8 bit A-Law PCM that can be used in case of ISDN but is not
recommended for PSTN, since it will cause an additional A-Law compression step in the test connection.
NOTE: The A-Law signal would be decompressed and fed as analogue signal in the local loop, where the regular
A-Law compression will be at the digital NTP or the PBX.
Today, ISDN/PSTN channels are narrow-band only. Thus, a transmission to an ISDN/PSTN end-point is always
restricted to narrowband despite that the airlink can use AMR-WB. The transition to narrowband is part of the gateway
to the ISDN/PSTN.
4.3 Narrowband and wideband scenarios
The analogue circuits of almost all mobile devices are able to process wideband or fullband speech. Whether a call is
transmitting narrowband or wideband speech depends on the wideband coding capability of the phone, the network and
call setup. The subscriber cannot control whether the phone connects in narrowband or in wideband. The established
channel determines the transmission bandwidth of the channel that can be narrowband, wideband, super-wideband or
even fullband.
4.3.1 Narrowband telephony and narrowband test scenario
The conventional narrowband or normal-band telephony is traditionally using a pass-band from 300 Hz to 3 400 Hz. In
digital transmission the technical limit is given by the Nyquist frequency due to sampling at 4 kHz upper audio
transmission limit; there is no limit at the lower boundary. Today's narrowband speech codecs as EFR or AMR are also
able to encode an audio band up to 4 kHz. Despite that fact, in practice a dedicated filtering is applied to the signal.
Usually, there is a bandpass that is wider than the traditional pass-band but still limiting at the lower and upper range.
The actual transmission characteristic is depending on the phone manufacturer and the setting of the phone. There are
no binding limits or characteristics.
Testing narrowband is not tied to a narrowband channel. Narrowband testing means that the listening quality is
estimated as listening through a conventional handset, the objective quality model filters the signal with such a
band-pass and compares the speech signal to an ideal narrowband reference signal too. This restriction to a narrowband
bandpass is applied despite the fact of the signal bandwidth passed through the channel.
For testing a narrowband scenario using a mobile access device there are two setups:
1) Insertion of a signal that exceeds the traditional narrowband bandwidth, e.g. 50 Hz to 3 800 Hz or even 50 Hz
to 8 000 or 50 Hz to 14 000 Hz. In this case, the limitation of the signal is done by the device and the channel,
while the device usually limits at most. At the receiving side, the recorded speech signal is compared to an
ideal narrowband signal (at a bandwidth of 50 Hz to 3 800 Hz). In this test case the filter characteristic of the
mobile device used has a significant influence on the estimated quality, since all restrictions to the reference
bandwidth are considered as degradation. The predicted MOS describes the overall quality as it is perceived by
the particular device and the channel; the score is device dependent.
2) Insertion of a signal that emulates a traditional sending path that is close to the defined passband of 300 Hz to
3 400 Hz. Therefore the test speech signal is filtered with a bandpass filter as e.g. IRSsend or MSIN. Usually,
those filters are narrower than the phone's characteristic. The phone's band limitations will not affect
significantly the speech signal anymore. By using such a setup, the filter characteristic of the particular phone
becomes less influencing. The bandwidth of the signal at receiving side is than wide
...