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| > Intrusive vs. Non-Intrusive Testing |
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Intrusive test methods, like PSQM and PESQ, insert a reference signal into the device under test. Like in a subjective test, the evaluation is based on a natural voice or music sample, typically of several seconds length. A stored reference is sent through the device under test, and the received listening quality is analyzed in comparison to the original. Using natural voice or music signals for the measurement is superior than applying artificial test tones, such as sinusoidal or noise, as they do not properly model the signal characteristics during normal operation.
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However, due to the fact that the reference signal has to be inserted into the device under test, such measurements are called 'intrusive'. For a telecom application this means that OPERA will generate test calls. From the perspective of a network operator, who's interest is in permanent network quality control, a 'non-intrusive' method, only based on single sided monitoring without generating traffic may sometimes be preferable. Such measures are also available but due to the missing information of the source signal, they are not as reliable and accurate as intrusive measures, but can be employed to derive a course quality indicator. Non-intrusive test methods will most likely not supersede intrusive analysis, but in the future, we expect to see a co-existence of both measures:
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A Non-Intrusive measurement, like 3SQM might be applied all the time for network quality monitoring. |
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In the fault case, an engineer would analyze what's wrong by employing an Intrusive measurement, like PESQ, to get most accurate results for problem diagnostic. |
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| > International Standardization successfully completed |
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In 2001 the ITU-T determined the need for a standard on non-intrusive voice quality measurement and announced an open competition in spring 2002 for the most accurate algorithm over a wide range of network conditions. Five companies declared their intent to compete. During the summer of 2003 Psytechnics, OPTICOM, and SwissQual agreed to combine their experience, expertise and individual models to create the best possible algorithm. Each company contributed their own algorithm, Psytechnics with NiQA, SwissQual with NiNA and Opticom with P3SQM (jointly developed with KPN). After a considerable testing and verification process the collaborative effort from the three companies was unanimously selected by the ITU-T as new recommendation P.563, released in May, 2004.
The joint algorithm, which is now available from OPTICOM as licensed OEM software under the brand name 3SQM, will open up new possibilities for network operators and vendors to determine the operational voice quality based on monitoring live calls. The benefit of this technology is that no test signal is needed and only one point of the telecommunication link is required to assess the voice quality.
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| > Download more detailed Technical Specifications |
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