VoIP MOS (Mean Opinion Score)

VoIP MOS Score, or Mean Opinion Score, is an ancient method of measuring voice quality in telecom. This starter guide covers why mean opinion scores are used to evaluate call quality, methods of calculating MOS score, as well as methods for improving poor MOS scores.

What is Mean Opinion Score (MOS) in VoIP?

MOS stands for Mean Opinion Score. MOS is a common calculation for tracking call quality in VoIP networks.

Why are MOS Scores used to test VoIP call quality? 

The MOS Score for Voice Quality was originally developed for traditional voice calls but has been adapted to Voice over IP (VoIP) in the ITU-T PESQ P.862.

The standard defines how to calculate MOS Score for VoIP Quality based on multiple factors such as the specific codec used for the VoIP call. Each VoIP codec (ex: G.711, G.722, G.723.1, G.729) behaves differently. Some codecs such as G.711 are uncompressed for higher quality but use more bandwidth than compressed codecs such as the G.729.

The MOS Score we measure is for the G.711 codec, which is by far the mostly used codec for VoIP calls.

How to calculate MOS score

The most important factor in measuring MOS scores is the caller’s perspective. Users identify good performance because essentially, good performance is the ability to meet a user’s expectations.

Quality of Experience (QoE) is a metric that allows you to measure performance from the end-user perspective to gain a better understanding of human quality metrics and be able to actually measure whether performance met a user’s expectations.

What is a good MOS score?

  1. Great: 4 & Above
  2. Fair: 3.55-3.99
  3. Poor: 3.55 & Below

Testing and Improving VoIP MOS Scores

VoIP travels a long distance from your network, through the Internet, and up to your Service provider. That means that, when a problem occurs, no matter where it is, you need to manage it.

Higher MOS scores should happen organically when you troubleshoot issues with your VoIP setup. VoIP Quality is about being able to get high-fidelity audio at each end of the phone call, without unwanted distortions. VoIP quality metrics will be most affected by: 

  • Bandwidth
  • Jitter (What is jitter?)
  • Latency (What is latency?)
  • Packet Loss (What is packet loss?)

A VoIP monitoring tool is the only way to accurately track voice quality metrics, especially on an ongoing basis. These tools may be included with your VoIP service. If not, 3rd party providers exist with tools that can be integrated into your existing system. 

VoIP Monitoring Software

AVOXI is a global VoIP service with it's own VoIP Monitoring feature. AVOXI VoIP Monitor measure VoIP Quality with MOS Score and start to proactive identify and troubleshoot VoIP issues before your users even know they exist!

Start with AVOXI’s free trial or contact us to schedule a demo.

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