Call Quality Metrics

Several standards are available for measuring telephone call quality.

• MOS measures subjective call quality for a call. MOS scores range from 1 for unacceptable to 5 for excellent.
  VOIP calls often are in the 3.5 to 4.2 range.
• The ITU P.861 (PSQM) and P.862 standards explain how to calculate MOS scores. The methods used require a test call in order to make the measurements. Kurittu and Mattila debate the practicality of P.862 for VoIP in an AES paper titled “Practical Issues in Objective Speech Quality Assessment with ITU-T P.862”. I can’t vouch for it because I couldn’t find it online for free, but there may be a few similarities with Takahashi, Hideaki, and Kitawaki’s Perceptual QoS Assessment Technologies for VoIP.
• ITU P.563 calculates call quality passively and calculates an R Factor that can be used to estimate a MOS score.
• Using the PESQ and PAMS call quality measurement methods require a license from Psytechnics a spinoff from British Telecom.
• Newer versions of Cisco IOS have built-in tools for measuring call quality metrics including estimated MOS scores for test calls. A detailed description of their methods is in this document: Service Assurance Agent (SAA) VoIP Proactive Monitoring.

For products to measure call quality see: How To Debug and Troubleshoot VOIP

See Also

• Passive voice quality analysis based on voice quality impairments detection. Non-intrusive waveform analysis to receive MOS score of call recordings and deliver information on the impairments that caused the quality loss.
• http://sevana.biz/recommended-voip-call-quality-metrics/|Recommended VoIP Call Quality Metrics]
• PESQ.org
• SoliCall Improving Audio Quality in VoIP Networks
• VOIP Troubleshooter
• Related ITU standards
• Recqual – Recqual (Real Call Quality) is an Asterisk based call quality tool that analyzes the round trip audio path.
• VoIP Spear — Web site that monitors your Internet connection 24×7×365 and shows you what your VoIP QoS is.
• http://www.voipmonitor.org — VoIPmonitor is open source live network packet sniffer which analyze SIP and RTP protocol.
• StarTrinity SIP Tester – Freeware SIP and RTP monitoring tool with G.107 MOS/R-factor, RFC3550 global max jitter, realtime charts and reports. Measures quality of live calls via mirroring port in passive mode, sends email alerts and daily reports. Active monitoring mode is not free, but it allows us to simulate calls and measure PESQ MOS.