The E-model Based Quality Contours for Predicting Speech Transmission Quality and User Satisfaction From Time-Varying Transmission Impairments

Document Type

Technical Report


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Publication Details

ITU-T Recommendation G.109 Appendix I, January 2007


This appendix introduces contours of speech transmission quality (or contours of user satisfaction) that can be used to predict speech transmission quality from time-varying transmission impairments. Quality contours are derived from the ITU-T E-model [ITU-T G.107] upon reducing it to the transport layer only (i.e., with assumed default values characterizing perfect terminals). The shape of quality contours is determined by the Delay Impairment Idd that covers loss of interactivity and the Effective Equipment Impairment Ie-eff that covers information loss due to encoding scheme and packet loss. The proposed quality contours determine the rating factor R for all possible combinations of packet loss (assuming a given encoding scheme) and mouth-to-ear delay (assuming echo-free connections). Quality contours can be used in cross-layer optimization of various communications layers (e.g., adaptive playout scheduling at the application layer, traffic differentiation at the MAC layer) when predicting end-to-end speech transmission quality from time-varying transmission impairments.