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Thread: What is MOS?

  1. #1
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    Question What is MOS?

    The Mean Opinion Score, or MOS (sometimes redundantly called the MOS score), is one way of ranking the quality of a phone call. This score is set on a five-point scale, according to the following ranking:

    5. Excellent
    4. Good
    3. Fair
    2. Poor
    1. Bad

    MOS never goes below 1, or above 5.

    Compressor/decompressor (codec) systems and digital signal processing (DSP) are commonly used in voice communications because they conserve bandwidth. But they also degrade voice fidelity. The best codecs provide the most bandwidth conservation while producing the least degradation of the signal. Bandwidth can be measured using laboratory instruments, but voice quality requires human interpretation.


    The MOS is generated by averaging the results of a set of standard, subjective tests where a number of listeners rate the heard audio quality of test sentences read aloud by both male and female speakers over the communications medium being tested.

    Different used codes in Phone call have different MOS as shown in below.

    Click image for larger version. 

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  2. #2
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    Hi all, way the meausered MOS decreased after handover and what can be the reasons?
    Best regards,


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  4. #3
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    When handover occurs, it needs time to setup call with other MSC and establishes traffic between MGw. That's the reason why MOS often decreases.


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  6. #4
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    Maybe different codec or bit-rate is used after the handover?


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    Do you any documents about MOS?



    Because I'm optimization but I'm not enough experiences.
    Please come to here and share


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