Calculation of the Mean Opinion Score of Telephone Service

## Calculation of the Mean Opinion Score of Telephone Service

### (Subjective & Objective)

Mean opinion score (MOS) is the most significant parameter of Quality of Experience of the telephone service, representing overall quality of a stimulus or system.

#### Subjective Measurement

Subjective MOS is the performance of telephone services (= speech quality) measured by reference to the answers of users / customers of the provider

The subjective measurement technique applies the statistical science and combines it with knowledge of ITU-T Recommendation P.830, 1996, which is a subjective method for quality assessment of broadband band and digital encoding aspects.

Subjective MOS = 4.5 is given if the customer thinks the quality of the conversation is very good, a value of 3.5 is given if the quality of the conversation is considered good, a value of 2.5 for moderate or sufficient quality, a value of 1.5 for poor quality, and a value of MOS = 1 is given if the customer cannot listen telephone conversation at all.

#### Objective Measurement

Based on the recommendations of ITU – T, there are two ways to measure the value of MOS objectively. The first is referred to Recommendation P.862, 2001, which use the concept of Perceptual Evaluation of Speech Quality (PESQ) is an objective method for assessing the quality of the conversation end-to-end narrow-band telephone networks and speech codecs, and the second is referred to the Recommendation G.107, 2014, which is a calculation of predictable sound quality as perceived by customers for telephone connection end-to-end using passive methods.

Telephony voice quality calculation procedure (using the R factor)

Where: (a) R0 represents the SNR (signal-to-noise-ratio), including noise sources such as noise circuit and room noise; (b) Is factor is a combination of all the distractions that occur simultaneously with the voice signal; (c) Id factor is a disorder caused by the delay; (d) Ie-eff (= effective equipment impairment factor) represents the interference caused by lower bit rate codec, and the disruption caused by loss of packet at random; (e) A factor is an advantage that allows the compensation of the factors that caused the disruption another advantage of the user access.

The Formula of R is

R = R0 – Is – Id – Ie-eff +A

Then the formula of Objective MOS is

MOSCQE (MOS Conversational Quality Estimate) formula:

– for R < 0; then MOSCQE = 1,

– for 0 < R < 100, then: MOSCQE = 1 + 0.035R + 0.000001R * (R-60) * (100-R) * 7,

– for R > 100, then: MOSCQE = 4.5

#### Information

• ###### Ro

The SNR (signal-to-noise-ratio), including noise sources such as noise
circuit and room noise

• ###### Is

A combination of all the distractions that occur simultaneously with the voice
signal

• ###### Id Factor

A disorder caused by the delay

• ###### Ie-eff (effective equipment impairment factor)

The interference caused
by the low bitrate codec, and the disruption caused by loss of packet at random

• ###### A Factor

An advantage that allows the compensation of the factors that caused
the disruption another advantage of the user access

#### Result:

• R Factor:

0
• Good Percentage (%):
0
• Not Good Percentage (%):
0
• MOSCQE (MOS Conversational Quality Estimate):
0
• Quality:
Null