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Friday TECHtionary.com Friday TECH-Tip – VOIP-QoS - MOS-Mean Opinion Score ExplainedThe animated tutorial is available at http://www.techtionary.com Summary This is a discussion of various types of QOS-Quality of Service related to testing of VoIP. Details This is a discussion of various types of QOS-Quality of Service related to testing of VoIP. Active (intrusive) monitoring refers to periodically or continuously sending test "acoustic ping" packets (PING-Packet InterNet Groper) across the network to compare against a baseline or reference sample. However, many testers believe that testing short tones does not reflect real-world conditions. Passive (nonintrusive) monitoring occasionally reviews desired and actual packet RTT-Round Trip Times. E-Model ITU-T G.107-108 or "Estimated/Estimating" value is designed as a passive method to quantify the voice quality of VoIP. The result or output of the estimate is the R-Model or Result/Rate/Rated Model. Here's where it gets complicated. The value of R can be correlated to the ITU-T-P.830 MOS-Mean Opinion Score. That is, MOS=5=R=100 or MOS of 4 (80% of 5) is an E-R of 80. MOS-Mean Opinion Score - is an international standard ITU-T P.800 uses a scale of 1 to 5 where above 4.0 is considered toll quality. E-R values range from 0 to 100. R is defined as Ro-Is-Id-Ie+A or signal-to-noise ratio minus speech impairment minus delay impairment minus equipment impairment plus access (wireline/wireless) transmission factors. PAMS-Perceptual Analysis Measurement System is a proprietary intrusive speech system designed to measure delay with a measurement scale of 1-5. PSQM-Perceptual Speech Quality Measure is an ITU-T P.861 standard scale of PESQ uses a 0 (zero) as toll-quality and 6.5 as poor quality (and there is no direct correlation to MOS/E/R). The PSQM algorithm (rule-of-thumb) is affected by CODEC compression algorithms, packet loss, packet sequence errors, echo, jitter and other factors. RTCP-XR-Real-Time Control Protocol eXtended Report is an eXtension to RFC3611 to report on jitter, total packet count, delay, packet loss and other factors. |