scope:

The present document proposes a way to model measurement results on a per sample basis that allow to estimate the perceived end-to-end speech quality per call for narrowband circuit switched voice services in mobile networks.

It focuses on speech (listening) quality of a voice call. Speech quality per call calculation determines the speech quality separate per each direction of the call. Conversational properties such as talker quality, round trip and other related metrics are not considered. Speech Quality of video telephony is not considered either.

The scenario is focussing on test signals between 60 seconds and 120 seconds in duration with alternating speech/silence periods as described in clause 5. The presented model is based on three studies but may not generalize to other call scenarios than those used in the underlying studies.

Throughout the present document where ITU-T Recommendation P.862.1 [i.2] (or ITU-T Recommendation P.862 [i.1]) is quoted the same applies to all measurements of listening quality. This can be listening quality scores gained by auditory tests (MOS-LQS) or objective measurements predicting MOS-LQO according to ITU-T Recommendation P.800.1 [i.3] covering the relevant network distortions and speech processing components in their scope.