Estimate Voice Quality - Nortel 1000 Description, Installation And Operation Manual

Page 198 of 644

Estimate voice quality

553-3001-363 Standard 2.00
ITG engineering guidelines
If the intranet capacity is tight and the IP Trunk 3.01 (and later) traffic
significant, consider making intranet measurements under load. Load can be
applied using traffic generator tools. The amount of load should match the IP
Trunk 3.01 (and later)-offered traffic estimated in "IP Trunk 3.01 (and later)
traffic engineering" on
The perceived quality of a telephone call is dependent on many factors, such
as codec characteristics, end-to-end delay, packet loss, and the perception of
the individual listener.
The E-Model Transmission Planning Tool is a model used to produce a
quantifiable measure of voice quality based on relevant factors. Refer to two
ITU-T recommendations (ITU-T E.107 and E.108) for more information on
the E-Model and its application.
A simplified version of the E-Model is applied to IP Trunk 3.01 (and later) to
provide an estimate of the voice quality that the user can expect, based on
various configuration choices and network performance metrics.
The simplified E-Model is as follows:
R = 94 – lc – ld – lp
where:
lc = codec impairment (see Table 30 on
ld = delay impairment (see Table 31 on
lp = packet loss impairment (see Table 32 on
Note: This model already takes into account some characteristics of the
IP Phone, and therefore the impairment factors are not identical to those
shown in the ITU-T standards.
September 2004
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