TTCs Standardization Work

1
TTCs Standardization Work
A Method for Speech Quality Assessment of IP
Telephony

• Network Management Committee

2
Establishment of WG on Speech Quality of IP
Telephony

• ?Work Group on IP Network Technology" of the
  Ministry of MPHTP pointed out the need for
  standardization of IP telephony speech quality.
• ?The TTC formed Special Working Group 7 under
  Working Group 4 (WG4-7)to study a method for
  speech quality assessment of IP telephony.

3
Mission of SWG2
?Standardize speech quality assessment method of
IP telephony ?Downstream ITU-T Recommendations
G series (Transmission systems) P
series(Telephone transmission quality) ?Contribute
to ITU-T Recommendations P series(Telephone
transmission quality)
4
Relations with Other Organizations
ITU-T Recommendation
ETSI TIPHON Implementation Rules
Downstream
Reference
Contribution
TTC Domestic Standardization
Reference
Reference
Opinions and suggestions
Reference
CIAJ Terminal Standards
VoIP Promotion Conference Application-Filing
Guidelines
5
Deliverables

• ?Approval in Sep. 2002
• TS-1001A Method for Speech Quality Assessment
  of IP Telephony
• ?Approval in Apr. 2003
• JJ-201.01A Method for Speech Quality
  Assessment of IP Telephony
• (presently TS-1001 ,
  extension of a scope )
• JT-G107The E-model, a computational model for
  use in
• transmission planning
• JT-G113Transmission impairments due to speech
  processing
• JT-G165ECHO CANCELLERS

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Purpose and Basic Policies of JJ-201.01

• ?The purpose of this standard is, taking account
  of the standardization trends of ITU-T and other
  organizations, to define a method of assessment
  with the total quality index, the R value,
  specified in the ITU Recommendation G.107 as the
  total quality index for IP telephony services and
  a method of assessment of parameters to
  complement the R value.
• ?For the purpose stated above, we made a study in
  keeping with the following policies
• (1) In principle, make sure that the standard
  conforms to related international standards
  (ITU-T, ETSI,
• and TIA standards), and ensure that it
  is consistent with international standards as a
  TTC standard.
• (2) Use the total quality index, the R value,
  for IP telephony services.
• (3) Specify evaluation conditions and method
  of assessment for the calculation of the R value.
• (4) In defining conditions and method of
  assessment, ensure the ease of assessment and
  fairness (strictness).
• The R value is the index calculated based on
  the E-Model, which has been developed as a
  network planning tool. Because of the facts that
  there are quality factors that cannot be assessed
  with the R value and that the verification of the
  correspondence between the R value and subjective
  qualities is not satisfactory, parameters to
  complement the evaluation based on the R value
  are necessary, so is a method of their assessment.

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Scope of JJ-201.01

• ? The following scope has been defined to
  maintain consistency with international
  standards
• Target services IP telephony services
  (including interconnection with existing
  telephone services)
• Quality type Speech quality. (Reliability,
  grade of service such as probability of loss and
  dial tone delay are not in the scope.)
• Time of application to a service Before a
  service is offered and while the service is
  operation.
• Terminal type "Handset" (voice signal
  frequency band 300 to 3400 Hz)
• Methods of assessment for
  terminals other than handsets are under
  consideration
• by ITU-T.
• The scope
  includes services using IP telephony software in
  terminals such as PCs.
• The fairness in
  measurement conditions will, however, be
  maintained by conducting
• measurement with
  handsets.
•  
• Methods of assessment Method of assessment of
  the R value in conformance with the ITU
  Recommendation
• 
  G.107 and a method of assessment of parameters to
  complement the R value
• Mapping between the R value and MOSs Mapping
  among the R value, the Western MOS,
• 
  and the
  Japanese MOS

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Characteristics of JJ-20.01

• ?Specifications to which revisions and additions
  have been made uniquely by the TTC
• Extensions of the packet size conditions
  assumed in G.113 Appendix I
• (extensions of the packet size conditions in
  G.729)
• The relationship between the Western MOS and
  the Japanese MOS necessary for conversion from
  the R value to conversational MOS
•  
• ?Provision of guidelines for a method of speech
  quality assessment
• Definition of reference configurations
• Identification of applicable network
  configurations
• Delay, echo, and listening MOS or PESQ as
  indexes to complement the R value

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Elements Making up the R Value
Concept The law of additivity of psychological
factors on psychological scale
No. of input parameters 20. The R value is
calculated from these input parameters.
R Ro Is Id Ie,eff A
Advantage factor Complements the effect of the
convenience of mobile or other communication on a
subjective quality (satisfaction).
Distortion/ discontinuity
A
Equipment impairment factor Represents subjective
quality impairments due to low bit rate CODEC,
packet/cell loss, etc.
Echo and delay
Ie,eff f4(Ie, Bpl, Ppl)
Loudness
Delay impairment factor Represents subjective
quality impairments due to talker echo, listener
echo, and absolute delay
Noise
Simultaneous impairment factor Represents
subjective quality impairments due to OLR
(loudness), sidetone, and quantization
distortion.
Basic signal-to-noise ratio Represents subjective
quality impairment due to circuit noise, room
noise at sending and receiving sides, and
subscriber line noise.
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Classification of R Value Parameters and Items
That Require Assessment

• ? The 20 R value parameters are classified into
  those whose defaults are used and those that
  require assessment to ensure the ease of
  assessment and fairness (strictness).

?JJ-201.01 clarifies the relationship between the
packet size and le,eff, that are not mentioned
in G.113 Appendix I, and expands the scope of
that Appendix.
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Parameters to Complement the R Value and a
Method of Their Assessment

• ? Problems with the R value
• (1) There are quality factors that cannot be
  assessed with the R value (such as burst packet
  loss)
•  (2) The E-Model has been developed as a
  planning tool, so that it cannot satisfactorily
• reflect the implementation
  characteristics of devices.
•   (3) The validity of the law of additivity of
  speech quality impairment factors such as delay,
  echo, and listening
• quality has not been sufficiently
  verified.
• ? To complement the total quality index with the
  E-model, the R value, a method of assessment of
  individual quality factors (parameters) is
  provided.
• Delay
• Echo
• Listening quality Subjective assessment
  (listening MOS value) or objective assessment
  (PESQ value)Note
• Note A method has been provided to suppress
  the measurement noise that affects the assessment
  value in PESQ
• measurement via an electric I/F with
  an terminal. The requirements on the noise level
  are also determined.