Objective Assessment Methodology for Estimating Conversational Quality in VoIP

Voice over IP (VoIP) is becoming one of the key technologies for telecommunications. Since IP networks generally do not guarantee transmission quality, it is extremely important to design and manage the quality of service (QoS) properly. To do this, it is desirable to develop an objective quality assessment method that estimates subjective quality based on the physical characteristics of the VoIP system. This paper first proposes a framework of objective models that can be applied not only to quality planning, which is an intended application of the existing standard methodology known as International Telecommunication Union—Telecommunication Standardization Sector (ITU-T) Recommendation G.107, “the E-model,” but also to quality benchmarking and management. Then, it proposes a model that complies with the proposed framework. Experimental results show that the proposed model has sufficient accuracy in the evaluation of practical VoIP systems. In addition, we attempt to integrate the opinion model with other objective quality measures, such as perceptual evaluation of speech quality (PESQ), standardized in Recommendation P.862 in ITU-T. Finally, we examine the task dependence of the performance of the proposed model.