Radio Frequency Engineering

Different types of Voice quality measurement systems and score evaluation (GSM and WCDMA)

There are different types of quality measurement system exist in telecommunication. For voice and video quality,  we use different types of measurement policy. But few standards are common and ratified by the different regulatory body such as ITU, ETSI, AT & T etc. During the measurement or testing procedure, we use different types of algorithm for different measurement system or different testing purpose. But among them few standards are very popular and vastly used for assessing the voice and video quality. Generally we can classify the measurement system into two parts one is subjective evaluation and another is objective evaluation.

Different types of voice quality measurement systems are given bellow:

ITU-T recommendation for voice quality testing

  • MUSHRA (Multiple stimulated with hidden reference and anchor) , In MUSHRA we use "lossy audio compression algorithm". MUSHRA ratified by ITU-R BS 1534- 2 and ITU- R BS 1534-3. It's a subjective evaluation system.

  • PSQM (Perceptual speech quality measurement) is such a measurement system  which allows automated and simulation based methodologies for rating both voice clarity and  transmitted voice quality. This system ratified by ITU-T P 861. In PSQM, we use a psychoacoustical mathematical modeling algorithm to analyze the pre and post transmitted voice signals. ITU-T already replaced PSQM(ITU-T P861) by PESQ (ITU-T P862).

  •  PESQ (Perceptual evaluation of speech quality) was developed as a model of subjective tests as per industry standard which will be widely used in Telecommunication system. It was standardized as ITU-T recommendation P.862 (02/01). Latter PESQ scores mapped into MOS score which was standardized as ITU-T P862.1. The scoring values of  PESQ SQI MOS(speech quality index mean opinion score)  ranges from 1 to 5 inwhich 1 means worse and 5 means best. The final score of PESQ SQI MOS is the arithmetic mean of all the tested scored.  
                    The thematic presentation of PESQ SQI MOS is given bellow:
Geographical distribution of PESQ SQI MOS Score from DT log 

  • POLQA (Perceptual Objective Listening  Quality Assessment) is the most recent ratified voice quality assessment system and best suited for wide band audio signal measurement. POLQA covers a model to predict a speech quality or alternatively we can treat it as digital speech signal analysis and rating procedure. POLQA was developed as per ITU- T 863 recommendation. It's the most widely implemented voice assessment system and excellent successor of PESQ (P8621). As like PESQ values POLQA scores ranges from 1 to 4.5. POLQA score evolution almost like PESQ. 1 means worse and the value equivalent to 4 or above 4 is excellent.
POLQA Reference vs Degraded audio signal

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