Copyright (c) 2013 Dublin Institute of Technology All rights reserved. http://arrow.dit.ie/commart Recent documents in Articles en-us Wed, 29 May 2013 12:20:20 PDT 3600 http://arrow.dit.ie/commart/2 http://arrow.dit.ie/commart/2 Mon, 24 Jan 2011 05:53:01 PST Delay and packet loss dramatically affect the quality of a voice-over-IP (VoIP) call and depend on the playout buffer scheme implemented at the receiver. The choice of playout algorithm can’t be based on statistical metrics without considering the perceived end-to-end conversational speech quality. The authors present a method for evaluating various playout algorithms that extends the Emodel concept by estimating user satisfaction from time-varying transmission impairments. This article evaluates several playout algorithms and shows a correspondence between their results and those obtained via statistical loss and delay metrics.

]]> Miroslaw Narbutt et al. http://arrow.dit.ie/commart/1 http://arrow.dit.ie/commart/1 Wed, 19 Jan 2011 08:22:20 PST 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.

]]> Miroslaw Narbutt