Overview on VoIP: Subjective and Objective Measurement Methods

In this paper we have carried out an accurate overview on Voice over IP QoS evaluation techniques. We have described in a detailed way the most important measurement methods that are subdivided in subjective and objective methods. Subjective measurements (e.g. Mean Opinion Score MOS) are the benchmark for objective methods, but they are slow, time consuming and expensive. Objective measurements can be intrusive or non-intrusive. Intrusive methods (e.g. Perceptual Evaluation of Speech Quality PESQ) are more accurate, but normally are unsuitable for monitoring live traffic because of the need for a reference data and to utilise the network. Non-intrusive methods, instead, are a measurement based on observing parameters that permit the individuation of voice signal quality. The possibility of having the telephony on Internet presents a lot of advantages, first of all it gives the capability of constructing a single network for transporting voice and data signals. Moreover, it provides the growth of new type of applications that can take advantage of internet network. At last, IP traffic charge is much less than traditional one because it is independent of the path length.