Dynamic QoS for commercial VoIP in heterogeneous networks

The R equation, derived by ITU for network planning that forms part of the E-Model (ITU-T G.107), has been the backbone of quality-of-service (QoS) prediction of telephony for decades and it has been very successful in predicting the Mean Opinion Score (MOS) and QoS for telephone systems. In this paper we question its applicability to Voice-over-IP (VoIP) systems and propose a preliminary VoIP-eM equation and research directions to examine this question. The issues to examine include the linearity of adding the disparate transmission parameters, the random assumption behind the packet loss and interpretation of I_d and I_e equation parameters representing impairments due to echo and delay, and impairments from transmission equipment, respectively. Further examination into the combined behavior of packet loss and packet delay, and other impairment scenarios including the environmental factors such as background conditions will also form a part of this investigation. In addition, demographics and languages spoken may show the variability in the R to MOS prediction and will therefore be investigated. The new QoS models will be evaluated for CODEC G.711, G.729, AMR, and GSM-FR. The proposed work will lead towards developing a dynamic QoS monitoring and active control system for the future heterogeneous VoIP networks.