Evaluation of multiplexing and buffer policies influence on VoIP conversation quality

This work presents a study of RTP multiplexing schemes, which are compared with the normal use of RTP, in terms of ITU R-factor quality estimator. The bandwidth saving of the different schemes is studied, and some tests with VoIP traffic are carried out in order to compare R-factor using three different router buffer policies. Network delays are added using an adequate statistical distribution. The tests show the bandwidth savings of multiplexing, and also the importance of the packet size with time-limited buffer policies. The customer experience improvement which can be achieved is measured in terms of R-factor, showing that the use of multiplexing can be interesting in some scenarios, like an enterprise with different offices connected via Internet.