Experimental investigation of the relationship between IP network performances and speech quality of VoIP

The paper investigates the relationship between IP network performance criteria and voice quality for VoIP service by means of extensive experiments on a test bed network. The IP network performance is examined in terms of the utilization of the bottleneck link and the following statistical factors for VoIP packets: the average of delay variations (jitter); the standard deviation of jitter; the standard deviation of packet interarrival times; the packet loss ratio. The experiments are performed by varying the following network related parameters: bandwidth of the bottleneck link; size of the bottleneck buffer; propagation delay; the average of data sizes transmitted. Statistical analyses of the experimental results reveal a high correlation between each of the IP network performance criteria and the corresponding voice quality. Moreover, the correlation depends on the bandwidth of the bottleneck link, but appears insensitive to the other network related parameters. These outcomes suggest that it may be possible to manage effectively the quality of service (QoS) of VoIP by monitoring the corresponding network performance criteria.