thinQmaster Virtual testing partner Adaptive practice exams that find your weak spots and drill them. Every answer explained. From $69
Enroll

thinQmaster

Find your exam

Five questions free, before you decide.

Step 1 · choose a vendor

In one of our camps? Your practice exams come with the tuition — they are on your study page already.

Collaboration, Voice & AV · Advanced

E-Model

The ITU-T G.107 transmission planning model that calculates an R-factor from delay, loss and codec impairments to predict call quality.

Definition

The E-model computes a transmission rating factor R from 0 to 100 by subtracting impairments for noise, delay, equipment (codec) and packet loss from a base value. The R-factor can be mapped to an estimated MOS, with R above about 80 considered good. Network monitoring and voice assessment tools use it to predict quality without listener tests.

Example

An R-factor of 93 maps to a MOS of about 4.4, while an R of 60 indicates many users dissatisfied.

Exam tip

If a question mentions an R-factor, link it to the E-model and to MOS estimation.

Related terms