The E-model
The E-model
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Advantage Factor
The "advantage factor A" represents an "advantage of access",
introduced into transmission planning for the first time via the E-Model.
This factor enables the planner to take into account the fact that users
may accept some decrease in quality for access advantage, e.g. mobility
or connections into hard-to-reach regions.
Provisional maximum values of Advantage Factor :
Bpl is the robustness of a codec to random packet loss. Tabulated values to be found in ITU-T Recommendation G.113.
Sources for circuit noise historically were associated with analogue networks using FDM systems and with certain switching systems. Only in special cases, e.g. interference to analogue cable sections by power lines or other noise sources, should noise be part of the planning calculation.
The D-factor is the difference in sensitivity (in dB) for the handset microphone between direct (voice) sounds and diffuse (room) sounds. D= STMR – LSTR.
This value shall not be modified.
The ambient noise at the talker's side.
The ambient noise at the listener's side.
Send Loudness Rating (for the E-model) is the Loudness Rating between the the mouthpiece of the talker's handset and the 0 dBr point (middle of the network) of the connection.
Receive Loudness Rating (for the E-model) is the Loudness Rating between the 0 dBr point (middle of the network) of the connection and the the earpiece of the listener's handset.
The loudness of a telephone sidetone path compared with the loudness of the Intermediate Reference System (IRS) overall in which the comparison is made incorporating the speech signal heard via the human sidetone path as a masking threshold.
The D-factor is the difference in sensitivity (in dB) for the handset microphone between direct (voice) sounds and diffuse (room) sounds. D= STMR – LSTR.
The loudness loss between a (diffuse) room noise source
and the earpiece of the handset (at the listener’s side) via the electric sidetone path.
T is the mean (average of send & receive direction) one-way transmission time
along the echo path, i.e. from the talker to the reflection point ("echo source").
Ta is the mean (average of send & receive direction) end-to-end one-way transmission time,
i.e from the talker's mouth to the listener's ear.
Tr is the round-trip transmission time along the whole echo path.
Talker Echo Loudness Rating is the the loudness loss between
the talker's mouth and his ear via the echo path.
Note, that in the E-model this refers to the listener's side.
WEPL is weighted mean value of listener echo loss, i.e. the level difference between the talker's direct voice signal and the listener echo.
Analogue/Digital and Digital/Analogue conversions involve a distortion of the signal, perceived as a quantization noise.
1 qdu is defined as the quantization noise resulting from a complete A/D encoding and D/A decoding following the 8 bit A-law (or mu-law), according to ITU-T Recommendation G.711.
Note, that the qdu concept is no longer used for coders other than G.711.
Probability of the occurence of packet loss.
BurstR is the so-called Burst Ratio, which is defined as:
BurstR = Av_observed / Av_expected
where:
Av_observed= Average lenght of observed bursts in an arrival sequence
Av_expected= Average length of bursts expected for the network under "random" loss
When packet loss is random (i.e., independent) BurstR = 1; and
when packet loss is bursty (i.e., dependent) BurstR > 1.
A scalar number allocated to a specific type of impairment (codec), indicating the anticipated incremental value of impairment (decrease of the transmission rating factor R) resulting from the type of impairment (codec). Tabulated values to be found in ITU-T Recommendation G.113.
Examples of Equipment Impairment Factor :
| Equipment/Codec type | Ie |
| ADPCM 32 kbps | 7 |
| ADPCM 16 kbps | 50 |
| LD-CELP 16 kbps(G.728) | 7 |
| CS-ACELP 8 kbps(G.729) | 10 |
| GSM 6.10 13 kbps, Full rate | 20 |
R is the result of the E-model, estimating users' satisfaction for transmission planning purposes.
An estimate of the result of a subjective test. Higher values indicate better quality.
Press this button to calculate the R-Factor with the above settings.
Press this button set all values back to default values.
Select one mode from the list.
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