A simulation study of adaptive voice communications on IP networks

This paper presents simulation results outlining the behavior of rate-adaptive voice communications over IP networks. In the considered architecture, voice coders adapt their rate to the current state of the network so as to generate only the bandwidth that the network is capable of carrying. An algorithm is proposed for driving the transmission rate of voice sources on the basis of estimations of the network conditions, measured in terms of packet delays and losses. The effectiveness of the proposed solution is then investigated in various scenarios which comprise: (i) a dedicated network in which the available bandwidth is exclusively shared between adaptive voice connections; (ii) a scenario in which adaptive voice sources compete with other TCP-like sources; and (iii) an uncontrolled network environment. We have compared the performance of the rate-adaptive against the non-adaptive (i.e. fixed-rate) approach for the transport of voice over IP. Using a rate-adaptive approach, more voice communications can be carried while maintaining a good quality of service, even on non-segregated networks.