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There are three factors that significantly impact call quality: latency, packet loss, jitter. We calculate the jitter using the Inter Packet Delay Variability (IPDV), see the [http://www.slac.stanford.edu/comp/net/wan-mon/tutorial.html#mos|http://www.slac.stanford.edu/comp/net/wan-mon/tutorial.html#mos][Tutorial|http://www.slac.stanford.edu/comp/net/wan-mon/tutorial.html#variable]. \[\] Most tool-based solutions calculate what is called an "R" value and then apply a formula to convert that to an MOS score. Then the R to MOS calculation is relatively standard. The R value score is from 0 to 100, where a higher number is better. To convert latency, loss, jitter to MOS we follow [Nessoft's|http://www.slac.stanford.edu/comp/net/wan-mon/tutorial.html#mos] method. the graph above shows the Exponetially Weighted Moving Average (using EWMI~i\~EWMI~i~ = alpha * EWMI~i-1\~+1~ + (1 - alpha) * Obs~i~, where alpha = 0.7). |
It can be seen from the above plot that VoIP ought to be successful between SLAC and the US, Europe, E. Asia, Russia and the Mid East (all above MOS = 3.5). S. E. Asia is marginal, S. Asia people will have to be very tolerant of one another, and C. asia and Africa are pretty much out of the question in general.
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