Performance comparison between VBR speech coders for adaptive VoIP applications

The recent introduction of new variable bit rate (VBR) speech coders has op ened up new perspectives for the implementation of Adaptive Voice over IP ( AVoIP) systems. The paper compares different VBR speech coding techniques i n scenario in which the rate of the single sources is dynamically adapted t o the workload conditions. The coders compared are the AMR, the M-3 R and t he G.729. Using source and rate control mechanism models, performance was e valuated in terms of loss probability, offered throughput and mean CMOS wit h varying numbers of sources. The use of header compression mechanisms was also evaluated.