A simulation study of adaptive voice communications on IP networks

This paper presents simulation results outlining the behavior of rate-adapt ive 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 alg orithm is proposed for driving the transmission rate of voice sources on th e basis of estimations of the network conditions, measured in terms of pack et 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 ba ndwidth is exclusively shared between adaptive voice connections: (ii) a sc enario in which adaptive voice sources compete with other TCP-like sources; and (iii) an uncontrolled network environment. We have compared the perfor mance of the rate-adaptive against the non-adaptive (i.e. fixed-rate) appro ach for the transport of voice over TP. Using a rate-adaptive approach, mor e voice communications can be carried while maintaining a good quality of s ervice, even on non-segregated networks. (C) 2001 Elsevier Science B.V. All rights reserved.